The base file
The starting point is a 24-bit stereo WAV file at the project's sample rate, usually 44.1 or 48 kHz. It is the format most digital distributors ask for. Avoid converting to MP3 or AAC yourself: platforms do that, and double compression degrades the sound.
Name your files clearly, with the track number, title and "master": "03_Under-the-rain_master_24-48.wav". This avoids confusion between versions, a frequent source of mistakes when releasing.
Loudness and normalisation
Streaming platforms normalise playback volume. They measure the track's integrated loudness in LUFS and adjust the level so that all tracks play at roughly the same volume. Reference values vary by service and listener settings, often around -14 to -16 LUFS.
The consequence: a very loud master will not be louder for the listener, it will simply be turned down, having lost dynamics. There is no mandatory value though: an electronic track and a jazz piece are not mastered to the same level. What matters is that the track sounds good once normalised.
True peak
When converting to compressed formats, peaks can exceed the maximum level of the original file and cause distortion. We therefore measure the true peak level, in dBTP. A margin of about -1 dBTP is common practice for files intended for streaming.
ISRC and metadata
The ISRC code uniquely identifies each recording. It is used to track plays and distribute royalties. In France it is assigned to the producer of the recording, either directly by a producers' society or through your distributor. A given recording keeps its ISRC; a new version, a remix for example, gets a new one.
The EAN or UPC code identifies the product, meaning the album or single as a whole. Prepare these codes, exact titles and the names of authors, composers and performers before mastering: we embed them in the DDP and the file metadata.
DDP for CD
To press CDs, the plant usually asks for a DDP file. It is an image of the disc containing the audio, track order, gaps between tracks, ISRC codes and, if you supply it, the EAN code. DDP avoids the errors of burning a master CD and is easy to transfer by link.
With the DDP we provide a checksum and a summary sheet. Check the track order and transitions before sending the file to the plant: once pressing starts, a mistake is expensive.
Vinyl
Cutting a vinyl record imposes physical constraints. Low frequencies must be centred, because very wide stereo bass makes the stylus jump. Excessive sibilance causes distortion. Running time per side affects the achievable level: the longer a side, the tighter the grooves and the lower the level must be.
For a 12-inch LP at 33 rpm, preferably stay under about twenty minutes per side to keep a good level. We prepare a pre-master per side, with the track order and gaps, and can talk directly with the cutting room about its requirements.
Checklist before sending
- 24-bit WAV at the project's sample rate, properly named.
- Level suited to the style, true peak under control.
- ISRC, EAN, titles and credits checked.
- DDP verified if you are pressing CDs.
- Pre-master per side and running time checked for vinyl.
- A full listen on several systems before approval.
Requirements change: always check the current specifications of your distributor, pressing plant or cutting room before sending.
