[ismarc]

I was on a medication that did something similar (I believe it may have been depakote or gabapentin). Thing is, I have absurdly good relative pitch, and combined with an 'internalized' sound of 60Hz (I've worked around a large number of generators and high voltage equipment over the years), I have the same net effect as perfect pitch (60Hz is roughly a quarter step above B-flat, a quarter step below B).

What bugged me was the intervals were off. It's hard to describe, but, for those not familiar with how the notes are laid out, 60Hz is quarter step below B, 120 is quarter step below B, 240 is quarter step below B, and so on. However, as you get higher, the frequency difference gets larger (B is actually 61.75ish Hz and B flat is 58.25ish Hz, next higher is 123.5ish Hz and 116.5ish Hz, and so on). Things were translated ~1/4 octave higher, which completely threw everything off because the 60Hz sound no longer fell evenly between two notes or even directly on a note, it was an 1/8th step away. This meant that as the notes got further away from 60Hz (higher or lower), the distance to the note got larger. So while everything was still evenly in tune, my guidepost began to really suck.

Long story short: I have no idea why it did what it did, but it was freaky. However, it was probably the most amenable side-effect I had from the medication.

[enf]

Did tempos sound faster too, or did just the pitches change?