This is my homemade sound system for sidewheeler I'm building. The speakers and amplifier came from unused PC system. It originally ran off 12V but I tried it on 7.4V and works just fine. The two black boxes are 30 second digital recorders from All Electronics($2 ea.) One has the whistle and the other has a calliope song on it. I had to modify them because you could hear a loud pop from the onboard record switch. Replaced switch with two pins that a remote switch can be attached to-no more pop. I am very satisfied with tone and volume.Will use one servo to operate both.