Generally speaking, iOS devices run the foreground app and any in the "background" are suspended. There are various exceptions such as receiving push notifications, gps navigation, recording audio, completing a task, etc.
@xxxsteveoxxx -- I'd argue that those 30+ apps weren't "running" as much as they had a saved "state" that they'd pick back up when you ran them again.
@PeteJames -- no idea about those apps; and from a quick glance at what they are, I suspect the question is better asked to the support groups / developers of the apps themselves as I'd guess there'd be more to trying to simultaneously run two different Abelton controller apps than just whether or not an ipad can run two apps.