I have just released a free musical toy/entertainment device.
Store link: https://play.google.com/store/apps/details?id=com.googlemail.pixelgoblinstudio.Goblin_DJ
Any feedback would be appreciated 
(Usage Note: the mix levels, chorus effect and speed/pitch effect are all applied in realtime, however if you change an instrument/loop the audio will change once the stop/play button is pressed again)