I cannot explain why I can do 7 or so recordings of a piano playing a song with no changes and yet some of the recordings will have feedback, of varying intensities, for no apparent reason. I am not an expert on Audacity but I enjoy the program very much and it is most helpful in recording the various parts of a song that is sung in Soprano, Alto, Tenor and Bass. perhaps some-one has had an experience similar to mine.
Is this regular-old acoustic feedback (squeal) where the microphone picks-up the sound from the speaker in a loop, or is it from inside the computer (where it’s more like a delay-echo)?
If it’s internal to the computer, make sure you’ve selected the microphone as your recording device (assuming you’re using a microphone)… Don’t use “loopback” or “stereo mix”, etc.
Tell us a little more about your setup… Are you monitoring the backing-track on headphones? Do you have an audio interface or are you using the microphone built-into your laptop, or a mic plugged into your laptop? Are you recording an acoustic piano with a mic, or an electronic piano with a direct-connection? Anything else you can tell us?