Cutting on the waveform
After you open a file, its waveform appears under the player: loud parts are tall, silence is flat, so you can see where a song starts, where a speaker pauses or where the applause begins. Drag the two handles to the part you want to keep. For exact points, play the file, pause where the part should begin and press Current position under Start, then do the same for End. You can also type times such as 1:05.5. The handles also move with the arrow keys once they are focused.
Play selection plays only the chosen part and stops at the end point, so you can check it before saving. Clicking on the waveform moves the player to that spot.
Fades and formats
A cut in the middle of music starts and ends abruptly. Fade in raises the volume smoothly over the first seconds of the selection, fade out lowers it at the end; the waveform shows the effect before you save. Half a second removes the click of a hard cut, two or three seconds sounds like a natural ending.
MP3 plays on every device. M4A (AAC) is a little smaller at the same quality and is the native format of Apple devices. WAV is uncompressed for editing, OGG (Opus) is compact and common on Android. If you cut an MP3 to MP3 or an AAC file to M4A without fades, the audio is copied as it is, so there is no quality loss at all.
Sound from a video
You can also open an MP4, MOV, WebM or MKV video. The cutter reads its sound track and saves only the selected part as audio, which is handy for a quote from a recording, a part of a lecture or a jingle from a clip.