
Introduction
to Mastering
An
overview of workflow and concepts
Mastering
is an essential part of the production process in ensuring that
what is delivered to your
audience is of the highest quality possible. It is also one of
the more misunderstood parts of audio production.
This section of my site offers basic information on the mastering
process and workflow for clients who are interested in how the
process works, those new to audio production, and those interested
in learning to master their own material.
Getting
A Mix Ready for Mastering
Before
discussing the mastering process I want to touch on a few tips
for getting a mix ready for mastering. These are very basic as
this is meant as an overview, so if you are a client with a project
I will be mastering, please contact
me for specifics in advance of sending your project for mastering.
Resolution
- Send your stereo mix in the same resolution as your mix session.
So if you mixed the project at 96/24, then send the stereo mix
at 96/24, do not down sample or truncate to 44.1/16 CD standard,
as this will be the final step in mastering. Whenever possible,
it is best to record and mix in 24 bit, as 16bit gives much less
headroom and resolution to work with.
Headroom
- A stereo mix should not be sent to mastering at its final volume.
Ideally there should be nothing on your master channel boosting
the volume of your mix, and it should definitely not be hitting
a limiter as this gives little to work with in mastering. Try
to have peak levels at no higher than -3dbfs (preferably more)
to give enough headroom for mastering.
Beginning
and Endings of Tracks - Leave plenty of space at the
beginning and endings of tracks, if there is a whole minute of
random noise before and after the track that is fine. Like headroom
this gives more flexibility, as a track that goes from digital
black straight into the music can be jarring. Also if there are
buzzing amps or other noises, do not mute these in the moments
before the music starts, if using noise removal there needs to
be a clean sample of the noise to make an accurate profile for
removal.
Live
Recordings - For live recordings, if possible send the
entire program whole, without taking out applause or dead time
between selections. These moments can be important in creating
a realistic ambiance for the album.
Use
Saturation and Effects in Moderation - While getting
just the right tone to your mix is important, keep in mind that
mastering can amplify these effects since the overall dynamic
range will be reduced. So if you are saturating almost to the
point of distortion or have crazy wet reverb, mastering may push
the effect over the edge into what does not work, meaning a master
may not be able to have the level as high as you may desire without
negative side effects. You can also add a limiter to your master
channel to reduce the dynamic range to get an idea of how some
of the more exaggerated elements will translate.
Listen
In Mono - A great mix will sound big and full in mono.
With most playback applications being in stereo the art of mixing
for mono seems to be often overlooked, but is an important part
of good audio fundamentals. If you hit the mono button and parts
of your mix disappear or the volume drops substantially, then
you likely have phase issues that will hurt the overall clarity
and quality of the sound. If you are not used to working in mono,
try it out, often if you are having trouble getting the balance
just right, try mono and you may be surprised how big it will
sound in stereo if it is well balanced in mono.
How
To Learn Mastering
When
leaning about audio production there is an abundance of information
on recording and mixing, but when
searching for information on mastering the most common response
I've seen is "just have a pro do it." So why
the exclusivity for mastering? Is it something only the elite
few can achieve? And what makes it so unapproachable to those
who love making music but do not do it as a career? Mastering
is like any other skill,
and can certainly be achieved with enough practice and study.
And this opportunity to get enough practice is where the difficulty
ultimately lies. Learning the aesthetics and technical aspects
of audio mastering takes a great deal of time and practice in
combination with having a highly developed ear that can discern
the many small details in program material as well as understanding
the sonic standards of many diverse genres of music.
So for an individual working on just their own material, having
the volume of work necessary to build this experience is going
to be difficult.
Personally before leaning mastering I had many years of formal
ear training as part of my background as a classically trained
musician, had studied thousands of recordings, and then leaned
mastering from an engineer with decades of experience. Even with
this training it was several years and hundreds of projects before
I felt that I could act intuitively when mastering and know that
I can approach any genre with confidence.
So for those wishing to learn about mastering, my advice is to
keep working and be patient with yourself. Mastering can very
easily do more damage than good, so begin conservatively. Do not
try to do everything at once, work with one element at a time,
and learn how each process effects the sound. Compare your work
to finished albums you like, and keep working to get closer to
them, first in tonal balance, and then later in level.
Pre
Mastering or Mastering?
The
process that has become known as 'mastering' is more accurately
called pre-mastering. The audio process
begins with the recording, this is then given to a mix engineer
who shapes the many individual channels of the recording into
a two channel stereo mix. The stereo mix is then given to a mastering
engineer who makes the final adjustments to the audio and creates
the pre-master. The pre-master is then delivered to the manufacturer
or digital distributor. This final process of creating the physical
master, or encoding the digital master, is technically mastering,
where the actual master for distribution is created. For the purpose
of this
article, pre-mastering will be referred to as mastering.
Metering
When mastering you will often be required to deliver material
that meets exacting standards for broadcast, distribution, video,
client request, etc. Additionally to ensure your material plays
back at safe and appropriate levels without distortion you will
need to understand proper metering as well as various broadcast
standards. Below is an overview of different meters I use when
mastering and how they are applied.
Decibel
- Definition -Before beginning the section on meters
we should first establish what exactly a decibel is since every
sound meter will most likely be in decibels. A decibel (deci-bel,
1/10th of a bel) is a logarithmic ratio used to define the the
ratio between two power quantities, like intensity or acoustic
energy. So for example an increase of 3db will be roughly 2X the
value of the source, while an increase of 10db will be 10X the
value. Since a decibel is a ratio, when using it in general terms
(when you see something expressed just as db) the ratio will be
from a given origin point. Decibels can also be used to describe
absolute values when they are attached to a fixed reference point;
you will see the reference after the db, such as dbfs, dbu, db-spl,
etc. When working with digital sound we will often see dbfs or
decibels relative to full scale, where the reference point of
odbfs is the maximum peak amplitude level in a PCM digital system.
Because this scale is referencing a maximum, its values are given
as a negative below this maximum point. When working with analog
gear you will often see dbu which references 0dbu = 0.775 volts
unloaded. If we are looking at loudspeaker output it may be in
db-spl which is referencing a sound pressure level of odb-spl
= 0.0002 dynes/cm2, or the threshold of human hearing at 1khz.
So you can see the decibel can be used to describe a large array
of different and not always compatible values, so while this is
a basic concept, it is very important in being able to understand
what our meters are telling us.
Peak
and True Peak/Inter sample Peak Meter - This measures
the peak level of your material. For mastering it is important
to use an over sampled meter that reads the True Peak or also
called Inter Sample Peak levels. Inter Sample peaks occur between
the samples, and can cause distortion if clipping occurs in a
digital to analog converter - aka - playback device. For CD my
max allowable peak level is -0.3dbfs, with a true peak max of
-0.2dbfs. For broadcast and Mastered for iTunes material the true
peak level should not exceed -1.0dbfs.
RMS
Meter - RMS (Root Mean Square) is basically the
average level. Its slightly more complicated than that, but for
our purposes this will suffice. In mastering since our peak level
will be near maximum most of the time, it does not give us much
useful information of the loudness of our material, so using RMS
levels gives us a much more meaningful figure. This can also be
used to determine dynamic range or crest factor, which is the
difference between RMS and peak level. If our peak level is -1dbfs
and the RMS is -20dbfs, then we have a large dynamic range of
19db; while a peak of -1dbfs and RMS of -6dbfs would be a very
small dynamic range of 5db and would sound much louder. Basically
the higher the RMS level, the less dynamic range in the material,
and the louder the material will sound. Before using your RMS
meter, check to be sure that it is compliant with AES specs, as
many meters out there will give readings that are off by as much
as 3 or 4db.
K
Meter - This meter was devised by respected mastering
guru Bob Katz, and is a combination of peak and RMS meters with
different zones specifying target ranges. There are three K Meter
scales: K-12 with a 12db dynamic range meant for pop and broadcast
material; K-14 with a 14db dynamic range meant for rock type material;
and K-20 with a 20db dynamic range meant for very dynamic material,
theatrical material, and classical music. In addition to mastering
levels the K system also includes specifications for standardized
monitoring levels. I find this a useful reference and utilize
many of Mr. Katz ideas in my mastering setup, however I do not
master strictly to this scale as I find it a bit too conservative
for the current mastering climate, as these scales will produce
masters that fall below the current expected levels and put my
monitor volume outside what I find comfortable.
Loudness
Unit Meter - LUs are close to RMS levels in that they
are both an average and will look similar on a meter, but the
LU is weighted using filtering to make it more useful for broadcast
material. An LU meter will generally have three different readings:
momentary, short term, and integrated. I tend to focus more on
the integrated level, as this will give an overall average for
the level of the entire song. For a rock album I generally have
a target integrated level of between -12lufs and -10lufs, depending
on the material. The standard for broadcast is -23lufs.
VU
Meter - A VU meter on your output will give you a musical
average and the needle ballistics can give you valuable information
about the actual level of your music. If you are having trouble
with balance, watch and listen for which element is making the
needle jump. For mastering rock and popular music styles I calibrate
my VU to 0VU = -10dbfs. For classical and acoustic styles it will
be lower, depending on the genre. Generally the meter should be
hovering around 0VU on the chorus or loudest sections.
Frequency
Spectrum Analyzer - Using either an FFT or RTA analyzer
will show the frequency balance of the material. While it can
be tempting to watch this meter when EQing your master, trust
your ears and use the analyzer to help identify problem spots.
Stereo
Analyzer / Stereo Oscilloscope - Used to reveal phase
errors. Phase problems are especially an issue for material to
be broadcast which should have a high degree of mono compatibility.
If phase errors are extensive and the material is highly out of
phase, I may ask if a remix is possible.
Spectrogram
- This shows a visual representation of audio in duration pitch
and intensity. I generally only use a spectrogram when working
to identify problems, such as feedback or intermittent noise,
from the audio.
While
meters are great tools, in the end its about how it sounds. While
I will often have targets to shoot for,
I still must individually evaluate the material. If I am shooting
for an integrated loudness of -10LU but
the material is very dynamic, I will need to reevaluate and aim
for whatever in the end produces the best result.
*
For more information on Loudness and metering I recommend the
materials available through the EBU
Website
Mastering
Workflow
This is a
step by step general walk through of my mastering process. This
is by no means The Correct way to approach a master,
but it is a workflow that I have found successful and it may give
you a starting point if you are working to learn. My workflow
is of course not limited to this, but this is how most projects
generally proceed. I will speak about concepts in general terms
to keep this to a reasonable length, but feel free to contact
me with any questions about specifics.
Analyze
the Material - Part of mastering is about quality control,
so when beginning the process the first step is to both look and
listen through the material and take note of problems. The problems
may include: phase issues, especially if the master is in stems
(separate stereo tracks for each of the groups - ie: vocals, drums,
guitars, etc); destructive noise like clipping, buzz, pops, clicks,
etc; and in the case of live recordings dropouts and intermittent
noises.
Once
these problem areas have been identified I will make the necessary
corrections before moving on toward addressing the musical issues.
Editing
- Any cuts and edits should be made at the beginning of the process,
as they can alter the level of the recording whenever a cross
fade is used. In general it is best to make edits in the mix phase,
as editing a multitrack source can be done more easily and transparently
than a stereo mix since each track can be spliced separately to
ensure the cut is optimally placed. However, transparent cuts
can certainly be made in the the mastering phase, but they must
be approached with care.
Listen
and Take Detailed Notes - Listen through the material
a couple times, focusing on specific issues on each listen through.
Taking accurate notes is important, as the human capability to
recall sound in detail is not as accurate as we would like to
believe. If the mix is overall in good shape and well balanced,
I may not need to write much as the process may be fairly straight
forward, but being thorough is important. This must be repeated
throughout the process.
Stereo
Balance - For most projects the goal is to have a recording
that sounds centered and balanced across the stereo image. This
may include adjustments to the left right balance, proportions
of the left and right side in the stereo image, and centering
of the focus point. If the material is off center, while it may
even sound ok on speakers, it will often sound much more exaggerated
and lopsided when listening on headphones. This is especially
an issue with classical recordings, where microphone and ensemble
positioning may make the ensemble weighted to one side.
EQ
- The most important concept for EQ in mastering is BALANCE. It
is very easy to overdo the EQ, cranking up the bass or treble
to get the sound really in your face, but when working to get
a great sounding master restraint is often the wiser course of
action. Start by listening for what is being obscured, and gently
cutting elements that are covering them up. I always begin by
cutting, as boosting runs the additional problem of increasing
the overall level, and taking away much needed headroom. The most
common problem I encounter is too much bass, especially sub bass,
in the mix. This is often due to a less than ideal monitoring
environment or incorrectly calibrated monitors at the time of
mixing. Or lets face it, some people just want to crank up the
bass. The louder you want your master to be, the more balanced
the mix will need to be.
In mastering automating the EQ is often necessary and can be a
more transparent way of working rather than picking a setting
that generally works for the entire song or project.
An example would be a chorus that needs to be livened up, using
a mid-side EQ with a high shelf to boost the high frequencies
on the side signal in just the chorus can help open it up and
give that extra sparkle needed to add excitement to the moment.
In mastering I use EQs with both Finite Impulse Response (FIR)
and Infinite Impulse Response (IIR) filters. These are more commonly
referred to as Linear Phase and Minimal Latency EQs. Each has
its pros and cons and uses in the mastering environment. A linear
phase EQ will not change the phase relationships of the frequencies
being altered, but introduces a pre ring distortion. The minimal
latency EQ may cause phase relationship issues, especially on
large changes, but its post ring distortion may be less noticeable,
making it a better choice for some applications. Until you learn
which EQ works best for you in varying situations, try both, and
choose whichever sounds best to you.
Dynamic
Control - aka - Compression
Contrary to popular belief, mastering is not about taking a mix
and crushing it with a compressor. While many mixes may have fallen
victim to this in the pursuit of the loudness war, many mastering
engineers are thankfully backing off this idea that the most hyper
compressed lifeless screaming loud mix wins. In reality I often
use little or no compression in mastering, and when I do it is
to correct an issue, or enhance the mix in a way that gives it
more punch or impact. Automatically compressing a mix can drastically
alter its balance, and compromise the musical intent of the mix
engineer. Below I will go over some of the basic types of compression
I employ in mastering, and their uses:
Downward
Compression - This is your basic compression. I often
will use very little compression at a fairly low ratio (around
2:1), compressing only 1/2 to 1db. This is done if the mix overall
is solid, but feels just a little bit loose. A very small amount
of compression can help solidify the mix and soften a few peaks
before leveling. If there is an element causing harsh transients,
like a snare that is too loud for example, I will use a very fast
compressor to reduce and even out the peaks. If the groove seems
a little weak and needs to be strengthened a slower compressor
can be used, emphasizing the the transients and giving the track
more bite. When setting the attack time listen for how the compressor
is effecting the transient, or attack of each note. It often helps
to over compress to exaggerate the effect letting you better hear
the adjustments, then remove the compression entirely and slowly
bring the threshold back down until you get your desired effect.
When setting the release you also need to pay attention to the
transients. If the release is too long the compressor will not
return to zero gain reduction before the next beat, dulling the
beat overall. If the release is too short it can result in a pumping
sound, or even in distortion. There are some genres where pumping
is desirable, such as dance or club music, but even in these settings
it should be used carefully as the effect can be distracting and
fatiguing to the ear when overdone.
Upward
Compression - Parallel Compression - New York Compression
- You can find all these terms basically meaning the same
thing, taking a copy of the mix and heavily compressing it, and
then mixing it with an uncompressed copy. Because all of the transient
information is retained in the uncompressed copy of the mix, this
can be a transparent way to add compression while not sounding
compressed. There are basically two ways I approach parallel
compression:
The first is the more transparent way of employing the technique.
Set the compressor to a very fast attack and med to slow release
with a fairly low ratio, around 2:1, and compress the mix heavily
until it is basically a uniform dynamic. Mix this in fairly conservatively
with the original, just until you hear the overall sound take
on more body and thickness. This technique is especially useful
with acoustic material where the softer elements need to be strengthened.
Overusing this technique can cause the sound to become muddy,
and can introduce distortion in the heavily mixed signal if clamped
down too much.
The second approach is similar to using a compressor to add bite
to the groove using just downward compression. Using a slower
attack and higher ratio, generally closer to 4:1, compress one
copy of the mix until you are getting a clear increase in its
transient clarity. You will want to compress a fair bit, but not
until the mix is completely squashed. Then mix the compressed
copy with the original, again be conservative, a little can go
a long way and it is easy to muddy up the sound if overused.
Multiband
Compression - Whether or not to use a multiband compressor
in the mastering environment is an often debated concept among
mastering engineers. I do not see any reason to exclude a tool
that may be useful, as long as I am aware of its limitations and
potential drawbacks. When used subtly it can help solve balance
issues or bring out an element without sounding boosted. A common
example would be a wind band recording where the mics were too
close to the flutes and pics, using a multiband to tame the high
frequencies without altering the rest of the balance. Be careful
when using a multiband compressor, as it can drastically alter
the balance of the mix, so I find it best to be used sparingly
and only when necessary. Also it is recommended to use a linear
phase multiband to reduce crossover distortion when working with
program material.
Expansion
- Using an expander can open up the mix if it lacks dynamic contrast.
When using an expander I find it most useful to automate it, using
it in select passages such as opening up the dynamic range of
a chorus. In general if you feel the mix is too compressed when
it is received in mastering, an expander can help add a little
life back into the mix, but it cannot work miracles.
Riding
The Fader - By far the most transparent approach to controlling
your dynamics, automate the master fader. In general I prefer
not to use compression on acoustic and classical music. If the
recording is balanced then all that should be required is to make
adjustments with the volume fader, but if the recording is not
properly balanced compression may be used correctively (ie - if
the brass are overbalancing the strings a compressor can correct
this imbalance by not allowing the brass to get as loud). But
in properly balanced recordings turning up the volume is soft
sections and then down in loud sections can control the dynamics
in a way that makes the music listenable while sounding completely
transparent and natural. My general rule with classical and acoustic
recordings is that you should be able to listen comfortably on
high quality headphones without having to adjust the volume throughout
the piece. Riding the fader is also used to enhance popular styles,
often boosting the chorus by as little as 1db can add a big sense
of impact, and bringing down a raucous outtro a little can keep
it from being pummeling and over the top.
Sweetening
- In mastering sometimes the sound or tone of a mix will need
to be enhanced. If a recording lacks warmth or depth, adding some
saturation, generally tube or tape, can smooth the edges and round
out the sound. If a mix is too dry and stark reverb can be applied
to give a little more depth. Reverb should be added carefully
and subtly, often using just early reflections can open up the
sound in a transparent way. Often reverb applied to an entire
mix will have to be aggressively shaped using EQ, and even compressors
and gates in some cases, as the various elements will not always
respond in favorable ways.
Fades,
Crossfades, and Other Creative Changes - All
creative volume changes, such as fade ins and outs, crossfading
between songs, fader rides, etc., should be made prior to the
leveling stage.
Leveling
- The moment we've all been waiting for - how do we make this
song LOUD!
With
so many new tools available and more powerful computers, its never
been easier to destroy a good album
by crushing it into submission with compressors and limiting to
make it loud enough to cause your speakers
to explode. Lucky the trend of hyper loud masters and the quest
for ever reduced dynamic range is starting to
reverse course. With more and more music going to a file based
format and being consumed through streaming services and online
broadcasts, as well as mobile hardware manufactures trying to
offer a better listening experience, the future is headed toward
loudness normalization. With loudness normalization, songs played
back to back will be lined up to playback at the same level using
their integrated loudness levels. So a hyper compressed master
will not sound any louder than a more moderately loud master with
more dynamic range. In this scenario the song with greater dynamics
will most likely sound bigger and dare I say... louder. Loudness
normalization will not alter the internal dynamics of a song,
so if the hyper compressed sound is something you desire, it will
not take that away.
So with this in mind, the following are ways to level your audio,
with some guidelines for how loud they should be. While this article
was written as a basic workflow guideline, when it comes time
to level the material many adjustments must often be made, so
the earlier steps will be revisited throughout the
leveling process to be sure the master remains balanced.
Limiting
- I am going to focus the discussion of leveling with brickwall
limiting, because it is the more widely accessible method for
raising the level of your music. Most DAWs will come with a basic
brickwall limiter, for example Pro Tools' Maxim, but be aware
that many of these offerings will not provide the same performance
as the more expensive tools aimed at professional mastering, so
listen carefully as it can be easy to push them past their usable
limits.
Start by setting up the output ceiling of your limiter. As stated
earlier, for a CD my output will be -0.3. Using a true peak /
inter sample peak meter you can be certain the max peak level
does not exceeded this, but if you do not have one and are unfamiliar
with the output characteristics of your limiter, ie - how high
will the inter sample peaks be for this type of material, err
on the side of caution and set the output to a lower level, like
-1db. Some limiters have many other settings, and for brevity
I will not go into other settings for limiting, but recommend
you take the time to carefully read the manual to get a better
understanding of the various settings and how they will effect
your audio.
Start adding gain to the material (or bringing down the limiter
threshold, depending on the setup) while keeping an eye on your
meters and targets. At this stage I find the VU meter most helpful,
as I get an idea of where the level stands musically. I
will want the needle hovering around 0VU (this will depend on
the calibration of the VU meter, which for me is generally 0VU=-10dbfs
for rock and around -18dbfs for classical) in loud sections, and
not getting too far into the red in the climax moments. I begin
by watching the meter because it can be easy to push too far if
not hitting the distortion point. The goal is not to push it as
far as it will go, but to reach the target level or where we will
get the best compromise of dynamics and level. Listen first for
distortion, if you are getting a lot of distortion at fairly low
limiting levels there is probably a buildup in the mid and lower
frequencies that may be addressed by going back to the EQ. Fine
tuning the settings of your limiter may also be required where
applicable, as there is no one size fits all setting. When using
limiters I have several different models that I use depending
on the application and genre. Next listen for the dynamics, more
specifically the beat or groove. A limiter works by removing the
tops of the transients, so the big downside is that limiting can
easily suck the energy and life out of a mix. At this point it
becomes a balancing act of EQ, compressors, and limiting to find
the optimum compromise where we are getting an exciting product
at a reasonable level. At this point I recommend using level matching
to compare the processed and unprocessed sound. Lower the output
ceiling so the output sounds the same when the limiter is switched
on and off. This way we can truly evaluate the final product,
we are easily deceived by the louder material, as our ear will
generally think it is better. It can be shocking to hear how bad
an over limited master can be when level matched with the original
source.
For
classical and most acoustic material, the peaks should not hit
the limiter with the exception of loud percussive sounds or hard
transients, a trombone rip in a brass quintet for example. The
level in a classical master should be controlled almost entirely
by riding the fader and careful compression, if your recording
is very quiet, go back and reevaluate choices in these stages
and do not push the material into the limiter so that the musical
peaks are being actively effected. The leveling stage should generally
be just about adding gain to bring the material up to the proper
level.
There are other techniques used in leveling to increase either
the average level or perceived level of the audio, such as clipping
(using a digital clipper or clipping a high end A/D converter)
and saturation. These are often genre specific, and I do not recommend
attempting them until you have a firm grasp of the basics. And
hopefully as we move back towards more exciting and dynamic masters,
these techniques will be required less often.
Peak
Normalizing - Peak normalizing measures the distance
from the highest peak to the ceiling (odbfs or a user specified
ceiling), and then increases the gain for the entire file by that
amount. I do not use peak normalizing and do not recommend it
because the peak levels often tell us little about the actual
loudness of the material, as our average level gives the most
accurate representation of loudness. If we peak normalize we may
end up with masters that are way off from the desired target volume.
A good example would be a recording of a harpsichord. The harpsichord
has a fairly limited dynamic range, when close miced generally
the difference between pp-ff in the low register is around 5db,
while the difference in the upper register is 1-3db. The harpsichord
also has a fairly low crest factor or peak to average ratio. So
if we were to normalize a recording of a harpsichord made at a
close distance to the instrument, the result would likely be in
line with a hot rock album. Just because we have available headroom
does not mean we necessarily need to use it all, as the material
needs to be presented in a way that falls within the normal range
for its genre.
Dither
- Dither is randomized noise (basically shaped hiss) added at
very low levels, ~-96dbfs for 16bit dither, to the signal which
modulates the least significant bit when truncating to a lower
bit depth. The result is increased resolution in the lower levels.
The max signal to noise ratio remains at 96db for a 16bit word
length but the actual dynamic range could be as much as 110-115dbs
as musical elements can be heard below the noise floor. This also
removes quantization distortion. A good way to visualize this
is by thinking of a sine wave. Without dither in a digital system
this wave would be blocky and square, like a sine wave made up
of stair steps, and by adding dither it will be smoothed out and
rounded. Dither is a rather complicated mathematical process,
but it is very important in digital audio and I recommend further
reading on the topic. The important thing to understand is that
dithering should be applied in the mastering stage as the final
process before truncating to a lower bit depth, for example if
your master is 24bit and you are reducing it to a 16bit CD format.
CD
Layout - Once the master is ready to be completed, if
you are making a CD you will need to lay out the track markers,
gaps, and CD text. If you are using a DAW designed for mastering
this process will likely be able to be completed within the same
program you have been working. If you are using a more generalized
production DAW, like Pro Tools for example, you can either create
the master by using a third party software plugin, or by bouncing
the file out and importing it into a stand alone CD authoring
program. iTunes or the burning software that comes bundled with
your computer are generally not suited for this task. To deliver
a master you will need software capable of CD text, ISRC, and
UPC codes as well as being able to create redbook compliant masters
and DDP images with MD5 checksums and CUE files.
CD
Delivery - To deliver your finished product meant for
CD to the client or CD manufacturer the two most common delivery
types are by a physical CD master or a DDP (disk description protocol)
Image, which is a digital file that contains all the information
for printing the CD. A DDP image is the safest and most convenient
way to deliver a CD, as the digital file includes data security
checksums to ensure it is recreated properly and it can be uploaded
directly to the client. A physical CD runs the risk of burning
errors, so after burning each copy it is important to run a diagnostic
to be sure any errors are within acceptable limits.
Encoding
- Because of music is now mostly consumed on devices that store
music in compressed files, proper encoding is an essential step.
Most large online distributors, like iTunes, will do the encoding
for you so you will need to deliver the audio in PCM uncompressed
format that is at least CD quality (44.1/16), and some will accept
high resolution masters (48/24, 88.2/24, 96/24 and up). For iTunes
they also have their preferred specifications which they refer
to as Mastered for iTunes (for more info: http://www.apple.com/itunes/mastered-for-itunes/).
If you are doing the encoding yourself it is recommended to use
software designed for mastering applications that will allow you
to identify masking at different bit rates and see where overs
are occurring. Whenever possible it is best to use the highest
bitrate possible when making Mp3s or other compressed files. While
all compressed lossy file types will be lower in resolution than
a master, this can be controlled and reduced with careful processing.
When lowering the bitrate to try to reduce file size, the higher
frequencies will be effected first. If you absolutely must deliver
small files, this can be compensated for in the mastering phase
with software that lets you audition the sound of different codecs
and bitrates. The biggest overall issue with encoding is overs,
or clipping. Encoding will generally raise the peak level of your
material, so you will need to lower it before encoding to be sure
that clipping does not occur. An Mp3 or ACC file that is clipping
will distort on playback, and can ruin a recording.
Encoding to lossless formats, like FLAC or ALAC, is much simpler,
as the quality of the master is retained.
Broadcast
- Mastering a project for release on the radio can be tricky,
as all stations will not process your material for the airwaves
in the same way and broadcast processing in general can be fairly
extreme. I have mastered both classical and rock material for
radio, internet streaming radio, including NPR, and streaming
video and in my experience have found that backing off compression,
concentrating on a clean frequency balance, paying special attention
to be sure the bottom end is not overly hyped, as well as enhancing
mono compatibility will yield the best results. For classical
projects I will use more manual gain correction with the fader
to keep the dynamic range more uniform, but will not lean on a
compressor. For rock projects I find that leaving the dynamic
range more open, especially if the CD master is hot, will make
it more yielding to broadcast processing. This may initially seem
counter intuitive, since broadcast is working with a limited dynamic
range and needs to ensure their material is listenable in higher
noise situations. But this can be equated to taking a hot compressed
mix, and then trying to compress it further; in my experience
I have found better results being more conservative and letting
the broadcast station crush it to their liking. When working with
material that is being sent for broadcast I also leave additional
headroom to give them room for conversion and processing. For
broadcast I send material with a max peak level of -1.0dbfs.
So
What Gear Should I Use?? - I have purposely left specific
gear out of this article, as the most important tools for mastering
are your ears and what lies between them. A good engineer can
coax a great sound out of whatever they have to work with, and
our audio forefathers made incredible sounds with a fraction of
the tools we have today. So if you are new to audio production
and are interested in mastering, start with what you have and
are familiar with, even the basic bundled plugins that come with
your DAW can produce fine results. As you progress and learn,
you will start to see what elements are holding your master back,
and then you can start investing in what you know you
need, rather than what some article, blog, or forum said you should
need. Just like learning a musical instrument, the first step
is a firm foundation in fundamentals. You could spend a fortune
on mastering gear and absolutely pristine converters, but without
an understand of the basics they will not do the work for you.
All that being said, if you would like to know what tools I am
using or what I recommend, feel free to contact
me, I like to talk gear just as much as the next guy.
I
hope you have found this informative and useful. I was lucky enough
to have mentors who were very supportive of me and who answered
my endless questions when I was first starting out, so now try
to return the favor for anyone interested in learning about audio
production.
So please feel free to contact
me with any questions you have.
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