AcaTech Series (1): Mastering 101 – What is Mastering?
by Dave Sperandio, Durham NC (USA)
Mastering, as it relates to audio or music, is a term that is often misunderstood or misused. If you do some internet research on the topic, you may hear mastering referred to as many different things, including both “mixing” and “black magic”. However, neither of these descriptions are accurate.
Mastering is a delicate, complex, and artistic process, but it is 1) not at all the same as mixing and 2) not magical in the slightest*. With a little effort, even a complete production novice can gain an understanding of what audio mastering is – and what it is not – and can thus be prepared to make better informed decisions about the use of mastering in music production. Let’s dive in, shall we?
What is mastering?
Mastering has 3 main parts:
1. Correction of sonic issues
2. Creative enhancement
3. Creation of media for distribution
At its core, Mastering is the final stage of audio production. It’s a mix or album’s final opportunity for quality control and corrective measures, as well as the last opportunity for creative input – ideally from an objective, uninvolved ear.
Mastering is the last chance for an artist to make sure a project sounds as good as possible – and sounds good on as many systems as possible – before its release.
How is mastering different from mixing?
Mixing involves taking all of your session or song’s audio, aux sends, and stems and applying compression, equalization, FX, level automation, etc. to each track, then bouncing or printing all of this down to (most often) a stereo file, or mix.
Mastering involves taking each of your mixed files (for instance, 10-12 stereo mixes), correcting (where possible) any sonic issues that are still present after mixing, making any final creative decisions (again, where possible; keep in mind that a mastering engineer is usually dealing with a stereo mix), and assembling the mastered tracks together as a sonically cohesive unit. This can involve noise reduction, equalization, compression, limiting, or other effects (*possibly even some “magic”), but these effects are typically applied on a “macro” level, to the entire mix (or to the middle and/or sides of a mix).
After this, the tracks are sequenced and spaced so that there is a continuity of sound to the project (so it won’t be necessary to adjust the volume or EQ when listening sequentially), and a final “master” is created. This “master” can be one digital file (DDP), multiple digital files (WAVs), or a physical product (CD/DVD). Once complete, the final ”master” is sent to be mass-produced / distributed.
What happens during the mastering process?
A typical mastering project may involve:
Setup – download and import of source material, sample-rate conversion, and labeling.
Auditioning – the source material is listened to, to evaluate and identify areas of focus.
Processing – the source material is processed as needed, and printed in real-time.
Sequencing – the mastered files are put in order and spaced appropriately.
Media Creation – the mastered files are exported/assembled as WAVs, DDP, or CD.
Verification – (aka “QC”) the final mastered project is auditioned in real-time by a separate engineer, to verify that no errors exist.
Distribution – the final, QC’d “master” is uploaded or sent via post to client or distributor, label, and/or replicator.
Archival – the mastered project is backed up, and all settings stored for future recall.
Can my mixing engineer also master my project?
An analogous question: can your family doctor perform a quadruple bypass, or a facelift? Probably, in a pinch! But do you want them to?
Mastering involves a highly specialized skill set and often requires years of learning and well-honed objectivity to “master”. The tools used to master are also extremely specific and usually quite different than those used by a mixing engineer, and the listening environment of a mastering studio must be exactingly accurate and reliable.
Even with the proper tools and environment, it can be difficult for someone intimately close to the project to be objective enough to be able to make the “forest for the trees” decisions at this critical stage. Objectivity is critically important at this stage.
Mastering is probably one of the smallest financial investments you’ll make over the course of your project, but it is also one of the most important and powerful ones, with great potential to help – or to harm. To give your project the best possible chance to achieve it’s full potential, it is recommended that you seek out a dedicated mastering engineer.
What do mixes sound like after mastering?
Professional mastering is often described as the “x-factor” which makes recordings “jump out of the speakers” and/or adds crispness, punch, clarity, and (often) loudness, while also smoothing out rough edges – subtle or dramatic – and making songs within an album flow together.
After your project has been mastered, you may expect to hear any of the following, as is applicable:
- More definition
- Added depth, width, or space
- Cleaner or punchier low-end
- More open top-end
- Less “mud”
- More present lead vocal
- Increased overall loudness and presence
- Less obvious distortion
- Mitigated phasing issues
- Reduced room noise, hum, or clicks
- Elevated awesomeness
How should mixes be prepared for mastering?
To maximize your music’s potential for enhancement, you should deliver your mixes as either multiple-mono or stereo-interleaved WAV files, in the highest native resolution possible. Here are a few Dos and Do nots:
Do not overly compress or limit your master fader / stems. Never worry about loudness!
Do not perform any sample rate conversion on your mixes.
Do not add any dithering to your mixes.
Do be sure to leave enough headroom for your mastering engineer to work with (-6dB is a good minimum starting point). Never worry about loudness!
Do make sure your mixes are truly “final” before they are sent to be mastered.
Short version: Just make your music sound as good as possible, fix as many issues as you are able to, and let the mastering engineer take care of fixing the rest and getting the levels competitive (again, a mixer should never worry about loudness).
What kind of guidance should I give the mastering engineer before starting?
Mastering can do a lot of pretty amazing things, and can sometimes absolutely “save” a project. But it’s not the same as mixing, so the feedback you give for mastering should be made with that in mind. Once your 192 audio and effects tracks have been bounced down to 1 stereo file (or one “mix”), there are certain things that mastering can do, and certain things it cannot do. Some guidance on feedback to give your mastering engineer:
Do say things like:
- Make Song 1 brighter / darker
- Make the bass louder on song 2
- Tighten up the bass on song 3
- Bring out the lead vocal on song 4
- Leave some dynamics in song 5
- Try to give song 6 some added depth / width
- Try to remove the room noise in song 6
- Just make it awesome!
Don’t say things like:
- Turn down the Guitars in song 1
- Turn up Florian in song 2
- Fix the solo tuning in mm32 on song 3
- Fix the T2 rhythm in mm8 on song 4
If you have questions about what you can and can not ask for, be sure to discuss with your mastering engineer before your mastering date. They will do all they can to address your concerns, even if that means recommending you go back and “fix it in the mix”.
Do I need a physical master (CD/DVD), a digital master (DDP), or just WAV files?
You may need one or all of these formats, depending on your plans for distribution. Please be sure to check with your replicator, label, or aggregator for their exact instructions. Here are some general guidelines to follow:
If you plan to replicate a CD (typically greater than 300 copies), most reputable CD plants will accept an upload of an exact digital copy of the project with all spacing added, called a DDP.
The advantages of sending a DDP are speed (no need to ship a physical CD overnight), cost, and increased reliability.
If you plan to duplicate a CD, (typically fewer than 300 copies – also known as a “short-run”, and essentially the same as you burning a CD in your computer’s CD drive), most CD plants will ask that you upload individual WAV files to their server.
If you require a physical CD to be sent to the plant (the plant should not *require* one, usually; this is a matter a preference for the client), or a reference CD to be sent to you, keep in mind that it will take more time, and there will be a chance for disk damage or shipping snafu.
If you’re releasing digitally, typically your aggregator will require you to submit WAV files.
Mastering a cappella music is especially difficult.The way sustained voices behave under limiting and compression is unique, and requires a highly experienced and delicate touch and a very specific set of tools to deliver maximum clarity and loudness while maintaining dynamics and musicality – without causing added distortion, smearing, or artifacts.
However, the payoff from having your a cappella music professionally mastered by a dedicated mastering engineer can be quite significant. In my next article, I’ll go into more detailabout exactly how your project can benefit from professional mastering.
– Dave Sperandio is the owner of Vocal Mastering, based in Durham, NC (USA). Recent projects include releases from Pentatonix, Peter Hollens, ARORA, Street Corner Symphony, Afro Blue, The Exchange, CASA (‘Sing’), and Varsity Vocals (BOCA).