I've just found out how to properly use the Garry's mod piano addon, i'm not the best but atleast i tried and that's what matters. If you have any experience with more complex songs then be sure to post them here, because i'd love to see it.
HL2RP servers were chock full of these, and it was brilliant. You could hear it across the entire city, and whenever anyone got off it there'd be a long line of speech going something like "djnsjaananasnkajnaajk;b'b mdln dm idjoaidjdlksanslkjadsn"