I've been experimenting in turd polishing.

I've found I can use noise reduction (NR) to remove all kinds of bad notes
as long as I have a moment of that note by itself to use as a sample.

Here's a situation where it absolutely won't work.

In a solo line the performer hits a wrong note but quickly moves to the
correct note with bits of the wrong note still ringing.

I can sample the missed note and repeat it enough times that the NR
software can form a model to remove. While just that note is being played,
it disappears nicely. When the "right" note begins it fails, however,
because the music line is not a simple sine wave. The overtones and
distortion on the right note serve to "activate" much of the spectrum and
push the frequencies I want to kill (of the wrong note) above their kill
threshold.

While the fundamental and lower overtones are gone, there's enough fuzz
left over to sound at least out of tune, if not ghosting the missing note.