The Thrill and Mystery of Delivering Files for Mastering
Updated: May 4
One of the most common questions I get asked is what files I use to work with in mastering, the differences between different file types and how best to export and deliver a mix ready to be mastered. This article is intended to be a guide to follow in answer to these questions. Please note that while I endeavor to be factually accurate on technical details, parts of this guide are in reference to my own personal preferences as an engineer and by no means represent the totality of opinion on any given topic. As always apply to your own experience.
A named stereo WAV file of the complete mix from start to finish, exported at the sample rate and bit rate you recorded at with no peaks over zero. That's it!
While this all you need to get started, further explanation of key details can be found below:
It's always very useful to have the track name clearly labeled on the file itself so that its easy to find and identify at a glance. Sometimes the artist name can be helpful as well if it has a very specific spelling or unusual characters. You would be surprised how often this important detail is forgotten.
WAV or AIFF files are perfect. MP3 or other lossy formats are not supported.
Whatever you recorded and mixed at, most commonly 44.1k or 48k, but higher sample rates are acceptable so long as they are the native sample rate you recorded and mixed at. There is no benefit to exporting a project at a higher sample rate than the one you recorded and mixed at.
Bit Rate & Dithering:
The technical ideal is to bounce any files for mastering at 32bit where possible, however 24bit or 16bit files are are also perfectly usable. 32bit files help solve potential headroom issues and eliminate the need for dithering.
If you do use a bit rate lower than 32 then you should apply dithering upon export. Any of the major varieties of dither suitable but should be applied as the final process before export, usually in the export screen itself.
Please ensure you export the entirety of the track length. A little bit of extra silence at the beginning and the end is always a good idea to avoid common errors or shortened decay.
Limiting, Clipping, Compression and Distortion: (all the fun stuff)
When mastering it’s important to me to minimise any unwanted or unpleasant changes to the mix I am working with. Part of this involves making sure the files I receive are in an appropriate format to work within the technical limitations of digital audio. The primary concern being digital clipping or limiting already present in a received file that can be extremely difficult or impossible to remove once present. The easiest way to avoid unwanted issues is as follows.
Turn off any limiters or compression you may have on the master bus. > Turn down the final output of your mix before export so that the signal does not exceed 0db on playback.
This method works for the vast majority of projects I receive and in any case where it doesn’t the problem can be simply identified and accounted for. In short if you aren’t sure what to do, give this a go and it should serve you well.
In cases where clients are more confident with their mixing ability and have chosen to use master bus compression or other processing on their mix I have no issue with receiving files to master that have compression engaged. This also applies to equalisation, saturation or in extreme cases even limiting. From my perspective I want to receive and work with the version of the mix that is closest to the intended final result and sometimes decisions made on the master bus at the mixing stage bus can be a big part of the overall sound of a record and can be difficult to perfectly replicate at the mastering stage if removed. In my case I’m happy to work with what sounds best to you as long as the files provided don’t clip on playback so that we can avoid any unintentional distortion. This is also a great example of a situation where reference files can come in useful.
I love to receive references, both of the completed mix or any other tracks you have been working on or have inspired your process. It can help a lot to know what you’ve been listening to and what you like about a given project so I can develop an understanding of what to enhance and what to leave alone. It is also useful to hear the mix you have been working with particularly in regards to understanding the intended final loudness for your project.
Loudness is a huge topic of debate in itself and every engineer has their own opinion, preferences and methods for achieving their desired loudness. Put simply, louder mixes tend to sound more impressive on first listen but can become fatiguing over time, there are also penalties involved on playback on certain services such as Spotify and Youtube and the tools we use to make masters louder have their own trade offs and consequences. Having said that, loud and punchy mixes can sound great when executed appropriately and it is my opinion that a balance can be achieved between what is considered “competitive” in the modern musical landscape and having a more open and dynamic master.
It is my view that the first priority of the mastering engineer should be the creative intentions and goals of the client and what sounds best for the given project. This has more to do with how a record feels when listened to than any specific metering targets or measurements. When mastering I try to take these points into consideration and provide a master that best represents the artistic intentions of the client and the conventions of a given genre or style as I understand them. The first guide for which is usually the reference mix or any notes provided by the client as the final loudness achievable for any given project is often more determined by the balance and nature of the mix more than what mastering can achieve alone. In short when provided with a given mix I will use my intuition to provide a master that I think represents the best sounding outcome for a given project. If you have any specific notes or directions beyond that please do not hesitate to let me know and we can have that discussion.
Stereo Mix vs Stems vs Tracks:
A Stereo file refers to an export of the complete mix via two stereo channels; Left and Right. This is the type of export required for a Stereo Master which is the most common type of mastering.
A Stem is an export of a group of instruments or sounds contained in a mix; such as All Vocals, All Drums or All Guitars. A Stem Master takes a number of Stems and processes them together to create a final Stereo Master file, the advantage of which is the ability to address separate areas of a mix as required to achieve the desired result. A Stem Master is generally a more labor intensive process than Stereo Mastering but can be useful in some genres and applications. It philosophically lies somewhere between traditional Mastering and the conventional Mixing process.
Tracks refer to individual instruments, sounds or recordings within a mix and are often confused for Stems. They can include both mono and stereo files from any number of sources and together make up the totality of a mix. They are not generally requested or required for Mastering but are the foundation of conventional Mixing.
A simple representation would be:
Tracks > combine into > Stems > combine into > Stereo Mix
That about covers the major topics of confusion or explanation I encounter around the topic of providing files for mastering. Thank you for taking an interest if you have chosen to read this far. If there are any areas that you think should be further expanded upon or that require a clearer explanation please do not hesitate to contact me at firstname.lastname@example.org