Multi-track tap screen sound app

Please tell me the name of an android app that turns taps on the screen into musical notes from different musical instruments (not just a drum kit). The program must have a piano keyboard/sequencer format that (1) assigns a particular instrument (voice) to the pattern that was tapped, (2) edits the pattern that was tapped by assigning the desired musical note to each tap, and (3) loops the patterns for continuous play and mixes the different patterns composed for a professional-sounding musical mix.
Thanks.