Your are missing a signal to your sound chip. One of the traces is bad or the chip behind that tells the sound chip which sound to make has a bad pin. So if it send 00101110 to the sound chip the bad pin or trace is dropping one of the signals and changing it to 00101010 or something similar so it plays a different sound than intended. So you need to check your traces to the sound chip to see if one is bad or get a scope and see if you are getting a signal out of all the proper pins on the chip that sends the info to the sound chip.