Merge audio
Merge several audio or MP3 files into a single track, one after another in the order you choose. Everything runs in your browser, the files never leave your device.
MP3, WAV, M4A, OGG…, you can pick more than one
What merging audio is for
Joining tracks is handy to create a single file from several recordings, assemble a podcast with intro and outro, concatenate audiobook chapters, or line up multiple voice clips into one track to share.
Files in different formats?
No problem: the tool brings everything to a common base, so you can merge MP3, WAV and other formats together, even with different sample rates. The order is the one shown in the list.
The problem is not joining, it is the jump between pieces
Two files recorded at different times almost always have different volume, and in the joined file the transition is heard as a step. It is the number one flaw of home-made podcasts: loud theme, quiet voice, loud interview again. It is worth listening to the join points before calling the work finished, because while editing you look at the waveform and do not listen.
The second jump is the background noise: two recordings made in different rooms have a different hiss, and at the join the change is heard more than the voice. In speech a simple solution is never to leave absolute silence between the pieces, because digital silence is unnatural and makes every seam obvious.
What happens to the files when they are joined
Different formats and sample rates are not a problem, but they are still brought to a common base: putting together a file at 44,100 samples per second and one at 48,000 requires a conversion, and it is worth knowing it happens. The same goes for a mono file and a stereo one: one of the two is adapted to the other.
What matters is the order, which is the one the files appear in on the list and not the one of their names. If the files are called «part 1, part 2, part 10», alphabetical order would put ten right after one: the classic mistake of files numbered without a leading zero.
How a podcast is assembled, in practice
The structure that works is always the same: theme, content, closing. The theme should fade under the voice rather than stop dead, and the volume of music under speech has to sit considerably lower than feels right while editing, because in headphones people tend to keep it too high.
It is then worth recording the parts in similar conditions: same microphone, same distance, same room. Thirty extra seconds of care while recording save an hour of adjustment afterwards, and no edit fully rescues two voices recorded in different spaces.
When it is better to stop here
Joining, trimming and adjusting volume covers most cases. If instead you need to overlay two tracks (a voice over a bed), apply a compressor, remove noise or place tracks on a timeline with effects, then a real audio editor is required: that is the boundary of this page, and it is better to know it before trying to force it.
For everything else, the advantage of working here is that the recordings never leave the computer: an interview, a lecture or a voice note is not uploaded to any server, which for unpublished material is the difference that counts.
Nearby tools
To trim a section there is Audio trimmer, to change format Audio converter and for speed Change audio speed. To record the parts Voice recorder, and for the audio of a clip Extract audio from video.