I think the sound could change Pparticularly when you imagine change the timming alot, you change the peak cylinder pressure, which changes the engines burn temperature, A/F burn rate, burn characteristics, and burnt/spent gas exhaust velocity, and, changing timing moves the peak cylinder pressure realitive to crankshaft, thus more "explosion" could spill out into the exhaust.
I agree though, I don't think it would change volume much, just characteristic a little bit.
