A free program for Android, by CV BungaHarapan.

Crossfader Dj Music Mixer is a professional Virtual DJ app that allows you to make your own party songs on your smartphone. You can use this app to seamlessly crossfade between two tracks as well as change the tempo and real-time pitch.

DJ Mixing is a popular and fun way to create music using digital music players. Using a combination of music tracks and the sounds that are available on your device, you can mix two songs together and create a new, unique song using a digital mixer. A typical DJ mixer will have several input channels that can be assigned to different musical instruments, like a piano, an electric guitar, or even a drum. Each channel will have an assigned volume and an assigned tone. The output of the mixer is a stereo or mono audio file.