Matched loudness
Each version is measured (ITU-R BS.1770-4) over the stretch it shares with the one you compare against, and its playback is trimmed to match. The files themselves are not changed.
The new mix sounded better. It was also a decibel louder.
ABA Compare — a tool in the ABA Toolbox, in prototype. It compares versions of one mix at the same loudness, so the choice is made on the mix.
Play two versions of a mix back to back and the louder one usually wins, whether or not it is better. A revision can be chosen for its level and nothing else.
ABA Compare takes the level out of the decision. Every version is brought to the loudness of the one you compare against and lined up with it in time, so switching between them changes the mix and nothing else. Then listen, switch, or pick blind behind closed doors.
Prototype
What “prototype” means here.
ABA Compare has been checked against generated mixes with known answers, and recovers them. It has not yet been run on a real session. It is on the site because it is usable as it stands, and it will change as it is tested; the build number in its header says which version you have.
The tool
Compare the mixes.
Drop in every version of one song, the earlier mix and each revision, and choose the one to compare against. The tool opens empty; its example loads generated mixes with planted answers, marked EXAMPLE on every row, so you can see a full result before you load your own.
Built for a desk and a pair of monitors: loading several mixes and listening closely work best on a computer.
What you get back
The level, the line-up, and what actually changed.
A blind test
The versions go behind numbered doors. Pick the one you like over several rounds, then open the doors and see which mix you chose, and how often.
What changed, band by band
A null test subtracts one matched version from the other. What is left is the difference, shown in third-octave bands and playable on its own, so you can hear what a revision really did.
The result downloads as a record: the full measurements, or a one-page summary in plain words for a client or a milestone sign-off.
What happens to your audio
It stays on your computer.
Your audio never leaves your machine. It is decoded and analyzed in your browser, and it is never transmitted.