A full version program for Android, by Contrasonic AB.

Chordbot is the most powerful and easy-to-use music app to play chords, experiment with chords, and create your own music. Chordbot lets you use any music keyboard to create complex chord progressions in seconds. It’s like a musical instrument and an audio mixer rolled into one. You can use it to create your own songs, and it’s all done in real time, so you can be sure it’s all going to be correct. 

It supports multiple instruments, including piano, guitar, bass, and even a few others. You can use as many instruments as you want, as long as they’re available in the app.