Heh, I just visualized my laptop keyboard transposed onto an 88 key piano, and then tried to imagine what a typical vim session would sound like on it...
Many MIDI virtual keyboard apps provide a mapping to the PC keyboard. Install one of those, (e.g. apt-get install vkeybd), plus a softsynth (e.g. ZynAddSubFX). Done.
I think tones in our hearing range would be a bad idea. From what I remember of my music theory class, our brains (through either nature or nurture) don't like discordant sounds like that for a long time. In fact, I believe it's been used as a torture device in the past, although I'm guessing it wasn't just a weird jumble of notes in that case.
I don't think I'd be very good at programming in any case.
EDIT: "a wireless, powerless keyboard where every key's click is tuned to a slightly different sound" hang on, like a piano?