A free app for Android, by KahvaltiZoo.

Virtual DJ Mixer – Dj Music 3D is a music-mixing app for Android. It lets you play two songs at the same time, with the option to add sound effects, change the tempo, add a fade, or split the audio in a crossfade. You can also set the volume of each of the two songs. The app also has a built-in equalizer with virtualizer effects. You can adjust the bass and boost the volume.

The app has a simple and intuitive interface. Simply select the two songs you want to mix, then select the effects you want to add. You can also choose to add a fade, or split the audio in a crossfade.