I do not have perfect pitch (cool party trick), but I can identify all 8 'normal' equal temperament intervals by ear relative to a reference (If you couldn't gu

I do not have perfect pitch (cool party trick), but I can identify all 8 'normal' equal temperament intervals by ear relative to a reference (If you couldn't guess, I play bass, which is a lame party trick). I was in Austria last year, and a bunch of the trains starting from a standstill had a "gradual acceleration" algorithm for their traction motors. As the drive frequency increased, you could hear the drive motor whine (or maybe it was the inverter?) along with the frequency. It was fascinating, because it played chords as it accelerated: root, 2nd minor, 4th major, 6th minor, octave, then it would pause at the octave and do it again after a few seconds until it reached max power I assume. Each chord had a very faint tritone added to it relative to the chord tonic, so you got this really harmonic pulsing. After the second course there was too much rail noise to hear what happened, but it was fascinating. I'll try to find a video, I know I recorded it. Power in Austria/Germany is delivered to trains via a really weird standard too: something like 25hz 27 kV. Leftover standard from 100 years ago.