So I've got this simple (33 second long) mp3 tune. It's pretty much a synth piano line, and a synth bass line. It's from an old video game. I'm planning on changing it around a bit. Nothing too much, just loop it so it's not so short, and perhaps add some layed back, simple drum beats. Does anyone know any programs where I could accomplish this? I'm new to this type of stuff. I've composed on the computer, but never remixed something this way. Any advice would be greatly appreciated. Thanks!