The idea
Keep a phrase, not the whole session. A short excerpt is easier to compare, share with a teacher or repeat during practice. The trimmer copies the selected decoded samples into a new WAV file; it does not remove noise or separate instruments.
Try it
Choose a recording you are permitted to process. Listen to the input preview and note the start and end times in seconds. For a phrase from 12.5 to 24 seconds, enter 12.5 and 24, then choose Trim audio. The output should be about 11.5 seconds long. Listen on the result page before downloading.
What to watch for
Keep start before end, and keep both within the actual recording. A cut through a loud waveform can produce a click; choose a quiet boundary where possible. Files are limited to 50 MB, five minutes and two channels, and codec support differs by browser. Conversion to WAV cannot recover detail already lost in MP3 compression.
Next step
Try another excerpt with a little silence before the first note. Compare both in your audio editor. The browser keeps your result for one hour on this device; download it if you need it later.