Mastering 101: Preparation

We’ve arrived to the last step in the mastering process: preparation.

This post is the sixth article in our introductory guide to mastering. If you’ve missed an entry, click on any topic below to catch up:

  1. What is mastering?
  2. Signal flow & metering
  3. EQ
  4. Compression
  5. Limiting
  6. Preparation

Let’s wrap up this guide by discussing a crucial yet often overlooked topic: preparation.

Part of a mastering engineer’s job is to successfully deliver masters in the deliverable format(s) requested by the client. Depending on where and how the music is going to be consumed, there are several file formats and delivery methods that you’ll need to take note of. Let’s go through some of the common formats and how you can assemble them for your client.

1. Standard file format for music streaming and online stores (Spotify, iTunes Music)


File format: WAV
Bit depth: 16-bit
Sample rate: 44.1 kHz

Preparing files for online music stores and streaming companies are pretty straightforward. All you would need to do is make sure your files meet the specified format. Here’s the steps I’d recommend you follow:

  1. Trim the starts and ends of each song so that when you press play, it starts right where it’s supposed to start and ends where it’s supposed to end.
  2. If you’re running a higher sample rate and bit depth than what’s specified (you should definitely be at least running a higher bit depth), you’ll need to sample convert / dither them accordingly. Most DAWs have built-in converters to handle this for you, but if you’d like to take it further, I recommend using a dedicated program to do it for you.
  3. Another crucial piece of info you’ll need to keep in mind is making sure that there are no bit-stream overs on your master. Most, if not all, streaming stores convert your music to either AAC or mp3 format, and you want to make sure your master doesn’t clip after it goes through the encoding. To ensure this doesn’t happen, you can use tools such as Sonnox’s Codec Toolbox to check for overs.
  4. Lastly, as a mastering engineer, you may be required to submit ISRC codes / metadata (artist information, album titles, track titles, etc.) to an aggregator. There’s no easy way to do this but to type it out and double check to make sure that there are no mistakes.
  5. If you’re helping an indie artist out (or yourself), aggregators such as TuneCore and CD Baby often offer you the ability to get ISRC codes for your tracks.

2. Mastered for iTunes (MFiT)

File format: WAV
Bit depth: 24-bit
Sample rate: 44.1 kHz – 192 kHz (project dependent) 

You can read all about the Mastered for iTunes format here, but rather than making you read a 10-page document on a file delivery format, we’re just going to summarize what it is and what you need to do to meet the specifications:

  1. Mastered for iTunes requires that you submit the highest possible resolution master if possible. That said, if you’re running a 44.1 kHz / 24 bit project, don’t up-sample your masters to a higher sample rate, as it doesn’t make any difference in any way.
  2. An important step in MFiT is ensuring that there are no bit-stream overs using Apple’s AAC encoder. Apple will reject your master if there are overs. Thus, it would be good to use a tool to help you check with the overs in advance.
  3. MFiT also recommends about 1 dBFS of headroom on your masters. Therefore, when you’re submitting files for iTunes under MFiT, you might want to re-bounce your masters to accommodate this specification.

3. Audio CD (DDP image)


File format: WAV
Bit depth: 16-bit
Sample rate: 44.1 kHz

If you’re submitting the masters to replicate on an audio CD, the pressing plant would most likely want a DDP (Disc Description Protocol) image.

A DDP image consist of data that holds all of your audio tracks, metadata, CD text, and ISRC codes. In order to make a DDP image, you would use a DDP authoring software. One of the best ones I know is by HOFA called the HOFA CD-Burn.DDP.Master. It’s a simple and straightforward DDP maker that allows you to easily make DDP images within minutes. All you have to do is line up your tracks, make sure you trim the start and ends, and enter all the necessary metadata for your track – that’s all there is to it.

The preparation process is a meticulous one. Make sure you triple check your masters before you submit them to an aggregator, label, or client. Mistakes usually aren’t forgiven in the industry.

This blog post concludes our six-part mastering series. If you have any questions or feedback, leave them in the comments below to let us know.

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March 7, 2016

Reuben Raman Product Marketing Manager at Splice