Not just one mastering format…There are many mastering formats used for delivering the music to the audience. If you’re confused with the number of master formats in the age of music digital distribution, you’re not alone! It gets confusing day by day, for both good and bad reasons. So, we have vinyl, cassettes, CDs, mp3, AACs…. It looks like any music service distribution – traditional stores (CD and vinyl), internet music stores, internet radio, satellite, has its own format, which is partially true.
The mastering engineers will ask you what master format you want, and when he mentions all the different formats, you decide for one, maybe two, thinking that later you can change the format. Sometimes it works, sometimes it doesn’t, therefore I decided to put together some info and try to explain in plain English the mastering formats types, so you can make an informed decision when you go to the mastering engineer.
What is the mastering doing?Mastering basically takes care of two important things:
1. Prepares the mixes for the audience while considering all the aesthetic decisions in regard to how the record is going to sound.
2. Adapt the mixdown to the delivery format that allows the listeners to enjoy the music. There are certain rules for each type of delivery format, and the mastering engineers prepares them accordingly.
The impact of the digital distribution.Most of the digital distribution outlets do not accept (want) encoded formats like mp3 and AAC, as they have their own procedures and processes, based on their tools; they create the master files themselves from the master you are submitting. What they really want is the so call “premaster”. And it better be at the highest possible resolution, preferably 24 bit/96 KHz.
You may still want your song in mp3 format, so you can use it in your website for advertisement. This is a very important aspect, often overlooked; a simple conversion from a CD (16 bit) or a 24 bit master to mp3 is not really the right thing to do for promotion purposes, it does not ensure the best quality. It may cost you a bit more, but you want your mp3 to sound as good as possible, otherwise there is no way the people browsing your site will want to go to iTunes or Bandcamp and buy your music.
Online stores like iTunes, Beatport, due to the large number of songs they handle, are using the services of aggregators, like Tunecore or CD-baby. The aggregators are handling the spreading of songs in the online stores and streaming services, including the preparation, so submitting a master in the best possible format is a must. A few examples of what internet online stores/aggregators are accepting:
- iTunes standard, Spotify, other online stores: 16 bit/44.1k wav files.
- Mastered for iTunes- MFiT: 24 bit / 96, 88, 48 or 44k wav files.
- CD Baby accepts CD-Quality wav.
- Tunecore accepts CD-Quality wav
- Bandcamp and SoundCloud accepts MFiT, basically 24 bit, sample rates above 44.1k
- Reverbnation accepts CD-Quality wav and mp3 at 320 kbps
- Rebeat accepts CD-Quality wav
- RouteNore accepts CD-Quality wav and mp3 192kbps
- Record Union accepts CD-Quality wav
The internet opened the doors of digital distribution. However, files in high quality (CD-Quality, and even better- the 24 bit files) formats are large, so digital distribution is done mostly with digital audio files like mp3 and AAC, which are much smaller. These formats are not lossless, and there are difference that can be heard between them and the premaster. As the network speed increases, we can see that the quality requirements of the internet stores and streaming services is going up; it's always a good idea to get the best possible resolution master.
When you are doing the mastering, you want to make sure that the mastering place uses a round-trip codec that allows the real time audition in the mp3 and especially AAC formats, to make sure these files will sound good. These codecs are AURoundTripAAC provided by Apple and Fraunhofer Pro-Codec from Sonnox. With them, you can hear how the files encoded off site (by iTunes, Tunecore, etc) will sound, and that is important. During the conversion, the encoded files will have audio glitches due to the inter-peak samples, so using these round-trip codecs detect the problems, and they can be corrected.
As I said before, asking for a mastered mp3 file makes sense if you need it for your website and promotion, but you may not do all the songs in an album, only what’s needed for promotion. However, with the future in mind, your best bet is to request a 24 bit/96 kHz master, or at least master with the same resolution like the mix (today actually everybody works at 24 bit, some at 44, some at 48, some at 96 and very few at 192kHz sample rate). If the mix is at 24 bit/48 kHz, do not ask for upsampling, it doesn’t do any good! 24/96 is the preferred resolution for iTunes, and the reason is that the codecs used perform better with a file at higher resolution. Even tough the CD file has 16 bit/44kHz, and the resolution is way higher than an AAC or mp3 file, the codecs will create a better file if you provide the higher resolution master than the file from CD.
At last, for vinyl the files should be 24 bit, with higher rates than 44.1 KHz if available, but 16bit/44.1KHz can be used too; and for cassette 16 bit and minimum 44.1 KHz (yes, I know, who needs them anymore?… actually they are coming back slowly).