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Combining recordings into one continuous file sounds simple until the clips have different sample rates, levels and formats. Add your files, put them in order, choose how they join, listen to the result and save a single track.
Processing locally on your device
Overview
Joining audio is mostly concatenation: the samples of file B are placed after the samples of file A. The catch is that every file must first share the same sample rate and channel layout. A phone voice memo might be 48 kHz mono AAC while a music file is 44.1 kHz stereo MP3. The merger decodes each file with the Web Audio API, resamples it to one output rate (the first file’s rate, 44.1 kHz or 48 kHz) and turns mono tracks into stereo when any track is stereo, using an OfflineAudioContext that runs much faster than real time.
Joins are where merges usually sound amateurish. You can place tracks back to back, insert 0.1–10 seconds of silence between them, or overlap neighbors with a crossfade of up to 12 seconds. Each crossfade is limited to half of the shorter neighbor, so a track’s fade in and fade out never collide. Five curves are available. Equal power, the default, follows a sine and cosine pair so loudness stays steady through the overlap; a linear crossfade dips by about 3 dB in the middle.
Level differences stand out more in a merge than anywhere else. The Match loudness option measures each track’s gated loudness (400 ms blocks with the BS.1770 gates, without K-weighting, so it lands close to LUFS) and adjusts it to a target between −24 and −9 dB, while capping the gain so peaks stay below −1 dBFS. The gain applied to each track is shown in the list. If the finished mix still peaks above full scale, for example where two loud songs overlap, it is turned down slightly to prevent clipping.
The merged waveform appears with numbered markers where each track begins, and you can preview it before exporting. Save it as MP3, M4A, WAV, FLAC, OGG or Opus. Decoded audio takes about 23 MB of memory per stereo minute, so merges of an hour or more are best done on a computer rather than a phone.
| Curve | Level at the midpoint | Best for |
|---|---|---|
| Equal power | About −3 dB per track, steady overall | Music to music |
| Linear | −6 dB per track (≈ 3 dB dip combined) | Short joins, similar material |
| S-curve | −6 dB per track, eased at both ends | Smooth, gentle transitions |
| Exponential | Outgoing track drops fast | Fading out a loud ending |
| Logarithmic | Outgoing track holds, then drops | Keeping the first track prominent |
Drop two or more audio files (or videos) onto the page.
Drag the rows, or use the up and down arrows, to set the playing order.
Choose Back to back, Gap or Crossfade, and set the length and curve.
Optionally turn on Match loudness and pick a target and sample rate.
Preview the merged waveform, choose a format and click Merge to download one file.
Use cases
Join an intro jingle, the main recording and an outro into one episode file. Turn on Match loudness so the music isn’t louder than the voices.
Combine several songs with 4–8 second equal-power crossfades so the music never stops between tracks.
Messaging apps often cut long voice messages into several files. Merging them back produces one recording that is easier to archive or transcribe.
Stitch chapter files into a single long track, with a two-second gap between chapters, for players that handle one file better than a folder of parts.
Pro tips
Answers to common questions about the audio merger.
Yes. Every file is decoded to raw samples first, so the original container and codec no longer matter. Clips are resampled to one rate and joined on a single timeline.
A gap inserts silence between two tracks, which suits speech and chapters. A crossfade overlaps the end of one track with the start of the next while one fades out and the other fades in, which suits music.
Each crossfade is limited to half the length of the shorter of the two tracks it joins, so a short clip can still fade in and out without its two fades overlapping.
It measures each track’s average loudness, ignoring silence, and turns it up or down to the target. The gain is capped so peaks stay below −1 dBFS, so a very dynamic track may end up slightly below the target rather than distorting.
There is no fixed limit. The practical ceiling is your device’s memory, since decoded audio takes around 23 MB per minute of stereo while it is being merged.
No. ToolEnhancer processes files on your own device inside the browser. They are never sent to, stored on or seen by our servers.
Yes. The audio merger is free to use with no sign-up, no watermarks and no daily limits.