1. for an augmented sense useful for musicians: add the ability to hear whether or not a note is in tune. Not sure how best to implement this — some sort of kinetic feedback system would be the most straightforward, but doesn’t seem true to it’s purpose in the same way that the belt buzzing north does.

    How about a small speaker on the shoulder/in a hat which plays a very quiet A 440hz — then use the beats to judge whether or not the note is in tune.

    Possible problems: might only work adequately for A and related notes (E, maybe D), might be irritating to have a constant sound — like artificial tinnitus. Also irritating if notes which the wearer doesn’t control are slightly out of tune! Probably the most simple solution is to allow the sound to be toggled quickly and easily.