OT: drum apps (iOS)?

[miden]

Just wondered if anyone here has come across drum apps for iOS that allow user selectable patterns - IE being able to randomly choose a main riff, or a fill or an ending for example and then have it play ad infinitum or until the user selects another pattern.

 

Or are they all simply cut and paste pattern operations and the onyl way to get these (fills variations endings etc) is to actually create a "fixed" song?

 

I discovered that Sampletank for iPad does have a sorta drum machine, but selection of a variation is "instant" no one bar wait time...and it is really difficult to get the tap at exactly the right time. Especially while playing