> By the end of freshman year, I had significantly expanded my musical tastes and unambiguously had perfect pitch… for piano only. I find it highly unlikely that this was due to identifying microtuning differences; I think the more convincing theory for instrument-specific perfect pitch is that one learns to recognize the timbres of the individual notes, not any minute variations in pitch. > Don’t learn a non-C instr…
Yeah, this advice doesn't hold up--even the OP mentions learning the clarinet, which is a B-flat instrument. I also play the clarinet and developed the same ability to detect each note by its timbre. I also think there is a kinesthetic element to each note--the way the instrument vibrates, the back-pressure or resistance you feel while playing, that becomes associated with the timbre the longer you play.
Interesting point. I had a similar thought about singing.
In theory, a good enough singer would be able to use their vocal chords as a reference. Unless their vocal range is changing on a regular basis, if they remember the highest piched note they can sing, they could refer to that as an anchor.