Audio Mixer Online

How the Audio Mixer works

Audio mixer online: how it works

Mixing is adding: the samples of every track are summed, moment by moment, into one file. It is how a voice ends up over music, how a sound effect sits under dialogue, and how two takes of a harmony become one. The only complication is that adding two full-scale signals gives one that is twice full scale, which cannot be stored, so the level has to be managed.

Level handling. Normalise peak to -1 dBFS is the default: the tracks are summed and the result is scaled so its loudest moment sits just below the ceiling, which guarantees a clean file at maximum level regardless of how many tracks went in. Divide by track count scales each track by one over the number of files, the classic safe mix that can never clip but that gets quieter as more tracks are added. Sum as-is adds the tracks with no scaling at all and clips anything that exceeds the ceiling; use it only when you know the combined peaks fit, such as a quiet music bed under a normal-level voice.

Balancing the tracks. This page mixes at equal gain. To make the music sit lower than the voice, run the music through the Audio Volume Changer first with a cut of ten to twenty decibels, then drop both here. To start one track later than another, pad its start with the Audio Padder. The file list only controls order for display; every track starts at time zero.

Mismatched files. Tracks of different sample rates are resampled to the rate of the first file, and mono tracks are placed in the centre when mixed with stereo ones. The output length is that of the longest track, so a short effect over a long bed leaves the bed playing on alone.

Memory. Every file is decoded in full, so the usual guidance of about an hour of stereo total applies. Mixing three five-minute songs is trivial; mixing six hour-long stems will strain a laptop.

Output. WAV 24-bit keeps the most resolution after scaling; MP3 at 192 kbps or higher is fine for a finished mix that will just be listened to.

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