AndroidCommute

Hello, I am new to composing music on my android phone, have been playing around with several apps: caustic, gstomper, rd3, etc. I know that most of these apps allow export in various formats.

My question is how best to sync and mix together tracks made in different apps. For example if I wanted to use drums from gstomper with 303 sounds from Rd3? The solution doesnt necesarrily need to be android based. it may make sense to use a desktop computer for this.

I see that many apps interface with soundcloud, but does soundcloud allow for mixing or only uploading complete tracks? Does anyone have any suggestions for a good synching and mixing app? Also is there any midi interface to an android phone that would allow me to control my music apps from a hardware keyboard?