Mastering for Apple Music: Sound Check, −16 LUFS and the −1 dBTP rule

Sound Check

Apple Music's Sound Check normalises playback to about −16 LUFS. Like Spotify, it turns loud tracks down and, within peak limits, quiet tracks up. It is on by default on iOS and in the Music app.

The practical result: a −9 LUFS master plays 7 dB quieter than it was made. A −14 master plays 2 dB quieter. Both end up at the same level as each other.

The Apple Digital Masters spec

Apple's mastering guidelines ask for 24-bit files at the original sample rate (44.1 kHz or higher), and true peaks no higher than −1 dBTP so the AAC encode does not clip. They do not require a specific loudness, but they do say to leave room for the encoder.

The −1 dBTP rule is the important one. Codec conversion adds overshoot on transients; a WAV that peaks at 0 dBFS can come out of AAC at +0.5 dBTP and distort on cheap earbuds.

One master for Apple and Spotify

You do not need two files. A master at −14 LUFS and −1 dBTP plays at full level on Spotify and is turned down 2 dB on Apple, which nobody hears in isolation. A master at −16 plays at full level on Apple and is turned up about 2 dB on Spotify if the peaks allow it.

If you have to choose, −14 is the better single target: more platforms use it, and the extra 2 dB of headroom in the Apple version is harmless.

* only when true peak leaves room.