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A/B your mix against a reference track, level-matched

A reference track is only useful if the comparison is fair. Match the loudness, compare the right passages, and keep the reference out of your master bus. Here is how, and how the tools that do it differ.

By Jean-Pierre Baroni, acoustic designer · 11 September 2026 · Français

Why louder always wins

Played back even slightly louder, a mix sounds fuller, brighter and more detailed. It is the same property of hearing that makes quiet mixes sound thin, explained in our guide to loudness compensation. In an A/B the louder side wins before the music is even considered, so comparing a mix in progress with a mastered release at their natural levels tells you nothing about the balance.

Formal listening tests align the level of whatever is being compared for exactly this reason. Your own comparisons deserve the same care.

Match loudness, not peaks

Peak level says almost nothing about how loud a track sounds. Use loudness in LUFS, measured to ITU-R BS.1770, the method behind broadcast and streaming loudness standards. A commercial master usually measures several LU louder than a mix in progress: bringing the two to the same reading is the whole trick.

Streaming services already normalise playback. Spotify, for example, plays tracks at around −14 LUFS by default. That helps, but your mix is not normalised, and normalisation can be switched off in the player, so measure rather than assume.

Match on the same kind of passage: a chorus against a chorus, a quiet verse against a quiet verse. Short-term loudness over a few seconds of comparable material is more useful than one integrated figure for a whole song that mixes both.

Choose references you can actually compare

• Same genre, similar arrangement. A sparse acoustic track will not tell you much about a dense rock chorus.
• Releases you trust on several systems, not only the latest hit.
• Two or three references rather than one, so you hear what they share instead of copying a single master.

Three ways to bring the reference in

Import the file into your DAW

Free and exact, but slow. Get the file, import it, turn it down until it matches, route it around your master bus processing, and remember to mute it before you bounce.

Load files into a reference plugin

Plugins such as Mastering The Mix REFERENCE and ADPTR Audio Metric AB sit on the master bus, take reference files, switch between mix and reference with the levels matched, and add analysis of tonal balance, stereo width, dynamics and loudness. The reference has to be a file you already have.

Take the reference from what is already playing

The newer approach skips files altogether and references whatever is playing on the computer: Spotify, Apple Music, a browser tab, another DAW. Matchbox's Stream AB does it as a plugin on the master bus, Sonnox ListenHub as a macOS monitoring toolbox, and PHON as a studio monitor controller that captures the application directly.

What changes when the reference stays out of the session

A plugin lives in the session: it goes with the project, and on the master bus it has to take care that your own processing does not colour the reference. A monitoring app sits after the DAW, so the reference never touches the session, and it works the same across projects, across DAWs, and with no DAW open at all. The trade-off is honest: a standalone app is one more thing to set up, and the analysis plugins go further into tonal balance and stereo.

A/B against Spotify with PHON, step by step

1. Set source A to your DAW and source B to the app playing the reference: Spotify, Apple Music, a browser, a video player or another DAW. On macOS 14.2 and later PHON captures the application directly, with no driver.
2. Play both, then press MATCH. PHON measures the two for three seconds to ITU-R BS.1770 and trims the source you are not listening to, so what you hear never jumps.
3. Switch with a click, a key or a MIDI button. Nothing is imported and your master bus is untouched.
4. If you work below your reference level, give the reference its own loudness compensation amount: it was mastered at a level you cannot know.

Common mistakes

• Judging before matching. Match first, then listen for balance, never for loudness.
• Comparing different passages. A chorus against a chorus.
• Running the reference through your master bus, so it gets your limiter too.
• Matching once for the whole session. Match again when you change reference or when the player's normalisation changes.
• Listening for too long on each side. Short, frequent switches beat long listens: memory for small tonal differences is short.