Thing is, Dennis, there isn't even a regular OS Chord sequencer app. So no chance of porting anything. Strange, considering how many utility and editor apps HAVE been user made for Yamaha's, Roland's, maybe even Korg's (don't know too much about Korg software). No-one yet has thought about a simple MIDI looper app.
Another app for iOS that might be useful is a very simple 'One take and save' MIDI Recorder for the BK series Roland's, which have no onboard sequencing or even a dumb one take recorder.
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An arranger is just a tool. What matters is what you build with it..!