This is my 'way off in the distance' wishlist regarding music functionality.
* I don't what they are called so will explain, be able to draw graphics in reaction to the music being played, a Visual Equalizer
* Change BPM on-the-fly to slow, speed up tempo
* Being able to change the Key of the vocal on-the-fly
* Audio Filters and other digital effect processing
* Be able to play one piece of the music at the same time.
I'd love to be able to have a user-definable period of time measured in seconds that two pieces of music can play on top of each other as one track ends and another begins. Perhaps (already doable) adding a crossfade between the two.
Playing multiple musics at the same time is planned. Equalizer support is also planned. The rest is not very likely at the moment but it might be possible using plugins some day.