I was discussing a mix with my son the other day. There was a bad resonance in one of the tracks that needed to be tamed - it was ringing over other stuff and was not pleasant on the ears
He did not have the option of rerecording as it was a set piece for assessment.
the resonance also changed pitch as the chords changed - the tone that was ringing out was in the octave above the treble clef (ca 700Hz to 2800Hz) and changed from C to B to A to D (2093, 1975, 1760, 2349) - being able to hear the octave the problem was in made it easier to narrow the pitch down. He identified the pitch range accurately (he said 800Hz-to 1500Hz, which is the octave of the notes that were played but the resonance was at the next octave up, kind of like a Santana sustained note that then feeds back at the octave harmonic)
knowing the actual freq of the problem notes meant that he could dial in a few notch filters with high Q (narrow bandwidth) and about 6db cut to take out the individual resonances without affecting anything else
