A free app for Android, by Data genius.

DJ Music Player – Virtual Music Mixer is the best music player for android phones and tablets. If you love to play music, but hate the fact that you can’t mix your tracks like a real DJ, then this is the app for you. This is a virtual mixing machine with 3D graphics and a full-fledged 3-band equalizer. 

It also allows you to mix and remix songs in real-time. You can choose any songs you want from your device and mix them. The app supports many popular formats.