Making: Circuit bending/broking

So I've obtained a cheap electric keyboard and taken it apart, testing the terminal jumps is a somewhat fustrating task, especialy you've killed something and you resultingly get only miniscule volume. oh dear (if worst case i'll just plug it into a amp and have a near mute, hissy, standard model. Ive found a few points that give a sine, but dont seems to cut out instead of change the pitch of the instument.