In mastering one of our main jobs is to deliver files that are technically compatible and that sound good, no matter what delivery format or playback system is used.
CD Masters are normally delivered to the plant as a set of files called a DDP (Direct to Disc Protocol). This includes the music in one file along with all the timing and text data.
If you have ISRC codes they can be included in the DDP metadata.
Also included is an MD5 checksum file that allows the factory to quickly check whether all the files have been transferred correctly.
There are no technical limitations to consider when creating a CD Master - we export files at 44.1kHz 16bit for the CD and eventually the CD Player will play back that exact data. When we and the artist are satisfied with that final sound then that’s the sound that will be delivered to the client on CD.
Most digital distributors and stores ask for WAV files at CD resolution, which is 44.1kHz 16bit. iTunes is one notable exception, please see our separate page for Mastering for iTunes.
This is a decent resolution however almost all online music stores convert the files to mp3 or other ‘lossy’ data compression for delivery.
There is no way of predicting how your music will sound coming back from all the different online music stores, however making sure the input file sounds excellent is a good start. Mastering World’s engineers have years of experience of mastering for all digital formats so we master music to translate well across all formats.
In most circumstances, the digital distributor that services the online music stores will also place your song on the streaming services, so the same master will normally do both.
As with digital, the default format is 44.1kHz 16bit WAV and most services will stream at less than this quality with lossy data compression. Some (like Tidal and Spotify) have options for higher resolution playback and options like these will only increase over time.#
As with downloads, there are so many destination formats and streaming systems that we can’t predict how your music will sound on all of these, but making the master file sound fantastic is a good start.
iTunes and Apple Music will accept files at up to 192kHz 24bit and will reduce the resolution depending on the output file requirements. Apple also supply tools for checking and auditioning that conversion process, and once those checks and adjustments have been done these files are referred to as MFiT (Mastered for iTunes) files.
Music correctly prepared for iTunes does sound better when played back or downloaded and these extra steps do give the music fan a subtly better listening experience. Please see our Mastered for iTunes page for a more detailed discussion.
Audio playback resolution on YouTube is not very high (128 or 192kb/s at time of writing) so as long as you’re uploading a video with 320kb/s audio you should be fine.
Where YouTube gets interesting is that it algorithmically adjusts the playback volume down according to the music’s volume. This means louder tracks will be turned down and the advantage of super-loud mastering is lost, because songs mastered with greater dynamics won’t be turmed down so much and will sound better than a super-loud song.
YouTube is a critical format for music distribution so this is another reason to master your music at a moderate volume rather than mastering for loudness at all costs.