A Guide to Mastering for Digital Distribution

by Rob Schlette

Mastering for digital distribution isn’t really mastering at all; it’s premastering. This article will help you know what to ask for from your mastering engineer.

The so-called ‘mastering’ process is actually two related, but operationally discrete sub-processes:

  1. Premastering, which encompasses all of the aesthetic decisions related to preparing a set of mixes for an audience. Premastering answers any questions related to what the project is going to sound like.
  2. Mastering, which is the process of creating the delivery media that will allow the audience to access the material. Mastering includes the creation of digital delivery media from the previously separate digital audio and consumer metadata resources.

Mastering for digital distribution isn’t really mastering, because the vast majority of digital distribution channels don’t want encoded deliverables like MP3, AAC, etc. They have their own internal processes, and in some cases proprietary tools, for creating (mastering) encoded formats themselves.

Digital music outlets like iTunes and Spotify, and the aggregators that connect independent musicians with them, want digital audio premasters. The table shows a selection of some of the most widely used digital distribution channels, and the premaster materials they accept.

MFiT CD-Quality wav FLAC MP3 (320kbps)
iTunes Yes Yes No No
Bandcamp Yes Yes Yes No
CD Baby Yes Yes No No
Tunecore No Yes No No
Reverb Nation No Yes No Yes
LANDR Distribution No Yes No No

‘Mastering’ for iTunes

In 2012 much ado was made over Apple’s Mastered for iTunes (MFiT) program, but most of the commentary failed to address anything that a producer or self-produced musician might actually need to know. Mastered for iTunes is two things:

  1. A detailed specification for providing iTunes or an aggregator with digital audio premasters (not masters). iTunes encodes the masters.
  2. A suite of simple tools that assist in the creation of those premasters. These include a simple utility that allows you to create AAC masters to audition.

What makes MFiT unique is that Apple is asking for high-resolution digital audio assets. Specifically, 24-bit wav files at the mix master source sample rate. Any specialized, professional mastering engineer working today should be familiar with these specifications. You can read about them in detail in Why Mastered for iTunes Matters.

Producers should be sure to ask for MFiT premasters from their mastering engineer.

CD Quality as a Rule

As you can see for yourself, the predominant request from digital music distributors is for ‘CD quality’ digital audio premasters. That is, 16-bit wav files with a sample rate of 44.1kHz.

Obtaining these premasters is easy, especially if the project in question is being released on CD. In fact, these are the same digital audio assets that your mastering engineer will use to prepare the CD replication master.

Be sure to ask for these as a discrete file set, as opposed to ripping them from a CD later.

An Example

Let’s say you’re planning on releasing your project with a limited CD release, and widespread digital distribution. This is a very common scenario. So, what will you need from your mastering engineer?

  1. A Red Book CD master in the form of either a hard copy CD-DA, or a DDP file set. This will be delivered to your CD replicator.
  2. A folder of the CD-quality premasters. These wav files will be delivered to the majority of digital music distribution channels – those that don’t accept high-resolution assets like iTunes.
  3. A folder of Mastered for iTunes premasters. These high-resolution wav files will be delivered to iTunes, and any other digital music distribution channels that have adopted the MFiT spec (or quietly emulated it).

It’s not hard to navigate the delivery specs for online music distribution, especially if you’re working with a specialized, professional mastering engineer. Be aware that there are, of course, additional specs and requirements for non-audio deliverables like metadata and album art. All of these are available online, and simplified by using an aggregator.