Shame its been abandoned
This is/was a terrific controller and general-purpose "jam" app for playing with ideas and sketching compositions. It gives you a broad range of tools and voices along with a well-implemented and expressive pad controller.
TJ got lots of details right. Although things have progressed a lot in iOS music space since its heyday, it set some standards and still holds them high.
I hope this dev or another revives this project.
jzipps about
ThumbJam, v2.4.2