Thanks for all the info, including the list of synthstation apps.

I think with MIDIBridge one can use SS25 with other CoreMIDI apps as well. (MB seems to be a useful app in general, a MIDI router.)

I will add that I think that Music Studio looks like a good MiniDaw, with MIDI as well as audio.

Thumbjam has some nice sounds, and I can play it with IRealB playing accompaniment in the background.

By the way, IRealB is not just a chart-displaying program, but an auto-accompaniment program like BIAB. It is the best one I have seen for IOS, much better than Chordbot. (I have bought both, not comparing the free versions.) Once one has bought it, one can download for free many charts for it from their forums. (One can also purchase additional sound packs for it at a low charge.) (I think an actual mobile BIAB would likely be much better, but that is not currently available. IRB is the best current one I am aware of.)

By the way, there is a version of the music notation program "Notion" available for Ipad (not Iphone nor Itouch though), currently only $6.99. (One wonders if mobile versions of Finale and SIbelius are forthcoming?)