Here's what I would like to do;
I would like to make a 2 channel DJ mixer with a display for each channel. I would like the displays to perform two functions. One, the displays would be used as an audio spectrum analyzer for the song playing on that channel. Two, the displays would be used to choose the mp3 file you would like that channel to play.
I would also like the board to have a female auxiliary port that way I can implement a cue function. The cue function allows you to hear the music playing on a channel before you decide to "bring it in" and turn up the output speaker volume on that channel. Basically, the cue function allows you preview a song before you decide to mix it in.
Sorry if this seems hard to visualize, but does it seem like it's possible with an arduino Uno? The DJ mixer would also include various knobs and buttons on each channel to modify and add effects to the songs being played.