I think it's just the game.
I tried it on both my MAME cab and my desktop computer (running MacMAME) and on both systems, the dip switch kills the sound effects, but the title screen still has that short bit of music.
I really liked this game too. It's just an original idea for a shooter. Of course, IREM is the company that designed R-Type. The vertical shooting also reminds me of Moon Patrol (also IREM).