The Roy Clark pin has chimes and stuff, which are cool, but I want to add some sounds to spice it up. Ol’ Roy is a great guitar player, and I thought it would be cool to add sound to things like coin up, game start, and some of the targets.
So, the problem you'll run into is that the game frequently doesn't do much during those events. For game start - how are you going to detect that? Every time someone pushes the start button? Well, that's going to cause problems when people press it mid-game, or press it several times in a row, or press it when there's no credits on the game.
Sometimes games have lights that only come on at certain times. You can use an optoisolator to drive a switch with those lights... but that's going to cause chaos if those lights do anything during attract mode. You could get around that by using the flipper enable relay to turn your sound board off and on, but now you're getting complicated.
Frankly, the only solutions I've seen that work have either replaced the chimes with a sound board (Gott Sys 1, the aftermarket PinTone boards) or it's basically been a computer that sits between the MPU and the sound board and intercepts the sound cues. Another option, if you just want beeps and bloops, is to use a Williams sound board and ground out the individual pins on the chips with various switch inputs.
Anyway, buy one of these and get to work, bro:
https://www.sparkfun.com/products/13660