Hi Peter,
Thanks for letting me know. Let me explain a bit how it works and maybe we can find out why it is not working for you.
1. midiArranger is using native Android MIDI to connect to and communicate, your device (or midi USB cable) must be "class compliant". There is a way to check this, in midiArranger go into Edit and see if you can record notes or play instruments when switching between midi channels.
2. midiArranger is indeed listening only on channel 1 for midi input (chord recognition, solo play with right hand, notes recording in edit). Are you 100% sure your organ sends the Key On/Off events on another channel? This is the first time I am hearing this, none of my users have this issue and I have more then 800 active devices. I know the standard is: midi channel 1 for keys and any pedals attached to the keyboard/organ.
Let me know, thanks.