MIDI note to Hz relation. Can it change? Is it an industry standard?

Where did you hear that? The two conventions start octave numbering for midi notes at -2 and -1, not 0 and 1. I’m quite certain the C4 SPN standard predates both the C programming language and MIDI.

I believe skijumptoes has the correct explanation for why there are the two standards. C4 has historically been middle C. However, Yamaha wanted the lowest note on the DX7 keyboard to be C1 instead of C2, so they adopted the C3 convention.

Guys, I wasn’t being serious. I just found the C / C language metaphor too tempting to leave alone.

Next time I’ll better bracket the humor. Or just take it up and octave and leave it out. :slight_smile: