this owner / builder Betelgeuse (pinside) of this machine has posted how he did the sounds with the MP3 trigger
"By popular request! I have finally got around to putting together a video of how the MP3 Trigger V2 was used in Ghostbusters to integrate the music, sounds and quotes into the game. I have had a lot of questions on how this was done and it's a bit difficult to explain through text, so I hope this helps. I have tried to cover everything, but I am sure there will be some details I missed, so please ask if you have questions. The game is still in a constant state of flux, so please excuse the crudeness of some of my work."Part 1
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Part 2
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sound good video of what the game looks like and how to wire up and run a MP# trigger system relatively easy. Also on part 2 a full game played out, a interesting watch.