Cut an MP3 or other audio file

How to use it#

1. Drop a sound file onto the box above, or click it to choose one.
2. Drag the two handles on the waveform to where the part starts and ends, or type the times. Press the waveform to play from that point.
3. Tick Fade in or Fade out if the part should start or end gently.
4. Play the cut in the preview, then download it.

A cut that loses nothing#

An MP3 is stored as a run of short frames, each about a fortieth of a second long, and the frames can be taken out and put back together without decoding them. So the part you choose is copied frame by frame into a new MP3, with no second round of compression, and it sounds exactly as it did in the whole song. The same goes for the AAC sound in an M4A and for a FLAC.

The cost is that a copied cut starts and ends on the edge of a frame, so it can begin a few hundredths of a second before the time you set; a FLAC, whose blocks are longer, up to about a tenth. Few people can hear that. A WAV holds every sample separately, so it is cut at the exact time and written out sample for sample, with nothing lost either.

Finding the part you want#

The waveform shows the whole file at once: tall where the sound is loud, flat where it is quiet. Gaps between songs, pauses in speech, and the moment a chorus comes in are usually easy to see, which makes the handles quicker to place than by listening alone. It also makes dead air at the start or end of a recording easy to trim off. The part outside the handles is greyed out, since that is what the cut leaves behind.

Press anywhere on the waveform to play from there. When you hear the moment you want, pause and press Set from player beside Start or End to take that time, or nudge a handle with the arrow keys, a tenth of a second at a time, or a whole second with Shift held.

Fades, and what they cost#

A part cut from the middle of a song starts and stops abruptly, which is fine for a sample and jarring for a ringtone or an alarm. Fade in raises the sound from silence over the first two seconds, and Fade out lowers it to silence over the last two. On a short part each fade takes at most a third of it.

A fade changes every sample it touches, so a faded MP3 or M4A cannot be copied. It is encoded again, at the bitrate the original was made at, which costs a little quality that is very hard to hear. A FLAC cannot be faded, because no browser can write FLAC again; to fade one, convert it with FLAC to MP3 first and cut that.