Good question.
I just got one too and the music goes tinny after a bit and then comes back (probably capacitors somewhere need replacing).
The sound effects seem too loud in relation to the music.
Also the music volume seems to go up and down, but I think that's by design as it seems to be quieter until you plunge a ball.
There might be separate boards or knobs for effects and music?
But my guess is like the Black Knight I had the music if probably on a separate ROM chip on the soundboard and need to be reseated