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Apple Digital Masters (formerly Mastered for iTunes)

Safe&Sound Mastering offers “Apple Digital Masters” as per Apple official providers list.

In the very first instance ensure your online music distributor can accept 24 bit audio files. This is very important, if they cannot you cannot have “Apple Digital Masters” compliant files.

Note: Most distributors for iTunes online will accept any audio files for sale on the iTunes platform. Apple Digital Masters is a very specific program developed by Apple to slightly improve the quality of sound from their AAC compressed codec. (And so Apple can store a 24 bit version of your music in their archives) You do not need ADM compliant files to upload to iTunes 16 bit – 44.1kHz masters are fine. If however the files are to be marketed as “Apple Digital Masters” and you are an “Apple Content Provider” then they must adhere to the guidelines using Apples mastering tools which I have here.

Having awareness of the possibility of ISP’s (especially those caused by loss-y file format encoders) means that I have been sending masters out with headroom below 0 dBFS for years prior to the advent of MFiT.

Being the major player in global music distribution Apple has recently decided to present some specific guidelines to mastering engineers to ensure the best quality is retained when a client uploads their files to iTunes. Apple have been working with a team of highly respected mastering engineers and produced a set of audio mastering guidelines specific to iTunes releases. AAC encoding has been around for quite some time but with the latest developments and improvements in their AAC encoding technology high resolution formats can be accepted.

The data compression algorhythm that encodes the AAC (Advanced Audio Encoding) files marginally benefits from a high resolution file upload. In short the AAC algorhythm uses a 32 bit floating point file which has immense headroom and protects against clipping and aliasing artifacts during the encoding process. AAC is a loss-y file format commonly used for the resultant downloaded files from the iTunes store.

Whilst the guidelines are technically specific it amounts to leaving a little more headroom during mastering for the encoder to work without causing what is known as ISP’s, Inter Sample Peaks. These peaks can occur during the encoder processing and cause a marginal loss of subjective fidelity. The guidelines also allow a secondary benefit which is that Apple will have a high resolution copy of your music archived and available if and when it decides to offer full resolution audio files for sale to the general public online.

If you require your music to have an extreme perceived volume please do not request mastered for iTunes. The goal of MFiT is improved fidelity for the AAC data compressed file format through increased digital headroom (along with maintaining original resolution of files presented). Very loud masters are contradictory to the goals of MFiT as we unable to use all tools possible for the generation of very loud mastering. Not all techniques for very loud mastering are permissible as they will not adhere to the guidelines presented by Apple.

File delivery requirements for “Apple Digital Masters”

If you would like your music “Apple Digital Masters” please send your files as follows:

Please send 24 bit files minimum, 32 bit float is also fine.

Files should be delivered at the sample rate of your project. Please do not “upsample” to a higher sample rate than your project as there is no technical advantage. 44.1kHz, 48kHz, 88.2kHz, 96kHz and 192kHz are all valid.

Please ensure the file does not have a limiter on it.

Please ensure the file does not clip the stereo master output bus. (especially important to check if you have removed a limiter)

An ideal level would be peaks in the file (identified as spikes in your DAW waveforms in the bounced files)  at -6 dBFS  –  6dB below the end of your standard DAW stereo output metering.

Delivered mastered files , post “Apple Digital Masters”

You will receive 1 set of masters at the same resolution and sample rate as the files that have been delivered to me with any additional tweaks specific to the guidelines for mastering for iTunes.

If you retrospectively require ADM files for your tracks this is chargeable as there is extra compliance work that needs to be performed. Similarly if extra non-ADM files are required this is chargeable. When you request a mastering job you must state in advance whether you wish for it to be MFiT compliant.

The compliance work for ADM releases requires additional work to be performed as per Apple’s Mastering tools as such there is a £10.00 per track fee added to the rates applicable on this page:

Please be advised that not all independent file distributors or online music distribution platforms currently support files above 16 bit 44.1kHz. So please confirm whether your chosen distributor can accept higher resolution formats. If you are uploading/submitting files to iTunes yourself then a high resolution format will be fine.

It is worth double checking with your chosen distribution platform if mastered files above 16 bit 44.1kHz are supported and you may find that some platforms will charge additional or escalated fees for dealing with the higher resolution file formats. Please make investigations before ordering files that have been mastered for iTunes. Generally speaking tracks that have been mastered for iTunes will also work well for high resolution, MP3 and site streamed releases.

Example prices related to Apple Digital Masters

  1. Track £40.00 (inc £10.00 x 1)
  2. Tracks £80.00 (inc £10.00 x 2)
  3. Tracks £120.00 (inc £10.00 x 3)
  4. Album £230.00 ( add £10.00 per track on album)

Note: Should alternative files be required in any event, such as different sample rates/perceived volumes I will provide a quotation on a job by job basis. I can also offer retrospective “Mastered for iTunes” priced per job. Please email me with your detailed requirements. (at being @ with no gaps)

If you would like to understand more about mastered for iTunes, respected mastering engineer Bob Katz has released a book about the process it is titled: iTunes Music – Mastering High Resolution Audio Delivery. I have a copy here and it is an interesting read for the technically minded.

Apple also has further information on their website: