RanSID - SID Runtime ANalyzer

Analyze this! Ransid is a tool for analyzing SID tunes -- how the tune is constructed, how instruments are constructed, etc. If you're one of these people who worries that their "secrets" might be discovered, well, get over it! A major reason this was written is that it is so hard to find information on designing instruments!

Technically, ransid works pretty much the way you'd expect: it maps RAM into the $d400 area, calls the player, then copies the result into a buffer. Once the specified number of SID "frames" are captured, it then provides a set of analysis tools for examining frames and registers, playing the tune, etc.

source

you might also want to look at the Iseq and all the other Commodore 64 projects from the Fridge.