What Sound Check does
Sound Check is Apple’s loudness normalization: the loudness of each track is measured, and playback is adjusted so tracks come out at about the same level. Like every service’s normalizer it is a playback gain change: the file you delivered is not altered. It works in both directions. Apple’s Digital Masters guide says the Sound Check information is used to “raise or lower the volume of each track”. So a loud master is turned down, and a quiet one can be turned up.
What Apple does not publish is how far it will turn a quiet track up. Spotify does: it lifts a quiet track only until its true peak reaches −1 dBTP, so a quiet master with high peaks still plays quieter than other tracks. So do not count on a quiet master being lifted all the way on Apple Music either.
Apple says Sound Check can also set the volume per album rather than per song, so the level relationships you mastered across a record survive; when songs are shuffled, each is leveled on its own. The general mechanics of loudness measurement (LUFS, gating, integrated versus short-term) are in What LUFS actually measures.
The practical consequence is the one worth internalising: on a normalized service, making a master louder does not make it play louder. It makes it play with less dynamic range at the same level. Every decibel of loudness you buy with compression is a decibel the normalizer gives back, and the compression stays.
Sound Check is a setting, not a guarantee
Sound Check is a listener setting, a switch in the Music settings. You cannot know, for any given listener, whether it is on.
Spotify is no different here. Its listeners can switch normalization off too. And Spotify says its web player and third-party devices, like TVs and speakers, do not use loudness normalization at all.
So on Apple Music, as on Spotify, a very loud master can play louder for part of the audience: the part with normalization off. That is the honest version of the loudness-war argument, and it is a much weaker argument than it first appears:
- It only applies to listeners with it off, and you have no way to know or influence how many that is.
- It costs you on everyone else. Listeners with Sound Check on hear the same level and less dynamic range: a strictly worse version of your record.
- Playlists are where discovery happens, and a track that only holds up when it is louder than its neighbors does not hold up in a playlist at all.
- It does not transfer. The same master goes to Spotify and YouTube. Spotify turns it down for every listener with normalization on, and people who measure YouTube report that it turns loud tracks down too.
Master the record to sound the way it should sound. That advice survives the setting being either way, which is the point of it.
Where the −16 comes from
- Apple Music, -16 LUFS integrated, ceiling -1 dBTP. Measured by third parties; Apple publishes −16 dB for Sound Check only in its podcast requirements, and asks for at least 1 dB of headroom in its Digital Masters guide.
Apple does not publish a loudness target for music. The -16 LUFS you see quoted is what third parties measure. The only place Apple itself writes −16 is its podcast requirements page, which says that with Sound Check on, content plays at −16 dB. The Digital Masters guide, Apple’s document for music, gives no loudness number. It asks for at least 1 dB of headroom, which is where the ceiling above comes from.
So treat the figure as an observation, not a rule. It describes where others have measured playback landing with Sound Check on; it is not a number to master to. A −9 LUFS master and a -16 LUFS master play at about the same level; the only difference the listener hears is how much dynamic range each has left. Because Apple does not publish the figure, nobody can tell you when it changes. That is one more reason not to master to it.
It is also worth saying what the target is not. It is not a minimum: a quiet, dynamic master sitting at −20 LUFS is not “wrong”, and nothing Apple publishes penalises it. It is not a maximum you will be rejected for exceeding: nothing refuses your upload for being loud. And it is not a mixing target. The number describes a finished master measured end to end, which is a different thing from where you set your faders. If those distinctions are new, mixing versus mastering is the place to start.
Albums are leveled as albums
Album normalization is the feature most worth knowing about, because it is the one that protects deliberate artistic choices, and because it stops applying the moment a listener leaves the album.
When a record is played in sequence, one gain adjustment is calculated for the album and applied to every track. An interlude you mastered 6 LU below the single stays 6 LU below the single. A record that builds from a whisper to a wall still builds.
Pull one of those tracks into a playlist and it is leveled on its own. The quiet interlude now sits beside tracks that were each leveled alone, which is usually not what it was for. Nothing is broken; the two contexts simply have different jobs, and it is worth deciding which one a given track is actually for before you master it.
What this means for sequencing
Master the album for the album, and check the singles as singles. If a track has to work in both places, the compromise is usually to keep its dynamics and accept that it plays quieter in the album context rather than to crush it so it survives a playlist.
What Apple Digital Masters actually is
“Apple Digital Masters” is not a loudness setting and not a file format you can select in a DAW. It is Apple’s certification program: mastering providers who meet Apple’s delivery specification (high-resolution sources, headroom for the encode, their validation tools) can be certified, and releases delivered through them carry the badge. The guide behind it is public. It is where this page’s headroom advice comes from; it gives no loudness number, so the −16 is not in it.
Following the specification’s advice is available to anyone; the badge is not: it belongs to certified providers, which is why you will not find it used as a preset label here or anywhere honest. The advice itself is sound engineering regardless of certification: deliver from the highest-resolution master you have, and leave the encoder room to work.
The badge is also not an audible quality tier. A certified delivery and an ordinary one of the same master encode to the same thing. What the program actually buys is a checked chain: that nobody along the way handed the encoder a file already reduced to 16-bit 44.1 kHz and squashed to the ceiling.
True peak and the encode
Apple Music streams lossy encodes, and encoding can reconstruct inter-sample peaks higher than any sample in your file. Apple’s guide also warns that oversampling on playback can clip a master that sits at full scale, and asks for at least 1 dB of headroom. The peaks that clip are the ones between samples, so read that as a true-peak ceiling (-1 dBTP). It is the strict number on this platform. A master that touches full scale on a sample-peak meter can clip inside the encode, on the version of your track everyone actually hears.
Why a sample-peak meter misses it
A digital file stores samples, not a waveform. The waveform is what those samples reconstruct into on the way to a speaker, and between two samples that both sit at −0.2 dBFS the reconstructed curve can rise above 0. Your DAW’s meter shows the samples; the converter, and the encoder, produce the curve. A true-peak meter oversamples, rebuilding the signal at four times the rate or more, to see the peaks that are only there after reconstruction.
Lossy encoding makes it worse rather than better, because the encoder discards information and rebuilds an approximation whose peaks land in different places from the original. This is why the ceiling exists at all, and why −1 dBTP is a floor for caution rather than a generous allowance.
This is the reason to measure true peak specifically, with a meter that oversamples, rather than trusting the DAW’s peak reading. Our checker measures it to ITU-R BS.1770, the standard Spotify names and Apple’s podcast requirements use, in the browser, without uploading the file. If the master is already distorting rather than merely peaking, the clipping detector is the one that tells you where.
Spatial Audio is a separate delivery
Apple Music’s Spatial Audio catalog is not the stereo master with an effect applied. It is a different deliverable (an Atmos master, authored from objects rather than channels) and it is measured and targeted separately from the stereo release.
Two consequences matter here. The loudness target for an Atmos delivery is not the stereo figure on this page, so do not carry the number across. And the stereo master is still what most listeners get, so it does not become a second-class citizen because an Atmos version exists.
What Dolby Atmos music actually is covers why object-based delivery behaves this way and why nearly everyone hears it as a binaural headphone render; our spatial audio page covers the render and export side.
−16 here, −14 there: does it matter?
Apple’s -16 and Spotify’s -14 look like a decision you have to make, and they are not. Spotify publishes its figure; Apple’s is a third-party measurement. Either way, each service sets its own playback level and adjusts your master on its own, and a loud master is turned down on both. There is no per-platform master worth making for loudness reasons alone; the Spotify page reaches the same conclusion from the other side.
The 2 LU gap does not change what you deliver. A master made 2 LU quieter for Apple would gain nothing: with Sound Check on, Apple turns tracks up or down to match each other. The real difference is quiet masters. Spotify publishes how far it will lift one, and Apple does not. The hub page, streaming loudness targets, has the full table across services.
Mastering for Apple Music in practice
Master the track to sound right, keep true peak under the ceiling with a real true-peak limiter, and deliver from the highest-resolution source you have: the encoder gets more to work with from a 24-bit master than from something already reduced. Let Sound Check set the level for the listeners who have it on; that is its job.
- Deliver 24-bit at the session rate. Do not pre-convert to 16-bit 44.1 kHz. Let the encoder work from the most information you have.
- Ceiling at -1 dBTP or below, measured with an oversampling meter, not the DAW’s sample-peak reading.
- Measure the finished file, not the mix bus in the session. Integrated loudness is a whole-program measurement and the render is what ships.
- Check the album and the singles separately if the record is being released both ways.
- Do not master to −16. Master to what the song needs, then measure. The number is a readout, not a destination. How to master a song covers the order the decisions actually go in.
Euphona’s mastering ceilings true peak at −1 dBTP by default, measured with oversampling, and reports the measured loudness and true peak of every master: the values the platform will see, not the ones the session intended.
The questions people actually ask
What LUFS should I master to for Apple Music?
None in particular. Master so the record sounds right and keep true peak under -1 dBTP. Apple publishes no loudness target for music. With Sound Check on, it turns tracks up or down so they play at about the same level, whatever you delivered.
Does Apple Music turn quiet tracks up?
Yes, Apple says it can. Its Digital Masters guide says Sound Check is used to “raise or lower the volume of each track”. What Apple does not say is how far it will raise one, or whether it stops before the peaks would clip. Spotify does say: it lifts a quiet track only until its true peak reaches −1 dBTP. Either way there is no penalty for delivering a dynamic master: the worst case is that it plays quieter than the tracks around it.
Will a louder master beat a quieter one on Apple Music?
Only for listeners who have Sound Check off, and only at the cost of dynamic range for everyone who has it on. Spotify is the same: its listeners can switch normalization off, and its web player and devices like TVs and speakers do not use it. The Spotify page covers what happens there.
Do I need a separate master for Apple Music?
No, not for loudness. One master serves every stereo streaming service. A separate deliverable is only required for the Atmos catalog, which is a genuinely different format rather than a different level.
Why does my track sound quieter than a reference on Apple Music?
Almost always because the reference has more dynamic range rather than less. With Sound Check on, both play at about the same integrated loudness, so what you are hearing as “louder” is usually a stronger transient and a more open mix: a mix problem rather than a mastering one. Genre matters here too; mastering hip-hop works through a case where the low end is doing most of the work.
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