For my children's shows I like to use light music in the background and needed to find a way to control it remotely. I also wanted to add some sound effects, so I was looking for a system that could do both. I recently tried out a solution that is simple, effective and cheap for those who own a laptop.
PowerPoint allows you to embed links to music tracks. A presenter's mouse allows you to advance the slides (move to the next track), some even let you control the volume up and down. You can set the laptop up where you can see the screen. Each PPT slide is linked to one track and is titled appropriately so that you just have to glance at the screen to know what track is playing. You can even add crib notes to the slide if it helps.
Using PPT allows you to stop the music without automatically moving to the next track and it lets you set the music so that it loops continuously until you signal it to stop ensuring that background music will play to the end of the effect.
A simple 1/8th jack fits into the headphone connector and the other end (RCA or 1/4# jack) goes to the amplifier. This has worked well for me and I thought I would share it with others.
If you are not sure how to set up animations in PPT just email me and I will send you instructions.