For example, using a program called AnimGet, you can (for example) rip sprites from Maple Story by capturing a tremendoua amount of screenshots and get the sprites needed per frame, then clean it up a bit to use it.
Whoops, wrong type of rip.
Midi rips uses a certain program to rip a midi from a game, which I don't know which or what.
It usually involves a simple process of "recording".