I'm very sorry about this
—
The current "App" Store version of Chordion no longer works on 5.1
—
do you have a backup of your iPad?
If so, restoring the backup should bring back the previous working version of Chordion.
If you end up getting a newer device at some point,
please let me know
and I can send you a promo code for one of our other apps.
Best,
Ben