what's the secret finger technique (iPad) for freezing a measure?

Whatever it is, I'm not present to it!
I have the chord/scale tool that displays the cord/scale info, measure for measure when playing and want to be able to freeze-frame it (touch the iPad in the area of the specific measure I just screwed up and stop it there)
By the time I get it to cooperate, the song's nearly over!
Help!
(I realize that touching the chord/scale chart freezes it, but I'm nowhere near fast enough to do that; I need to go back a couple measures to get to my problem, and that requires effectively touching that measure to recover and freeze that scale/chart)

Yes you just have to stop and long press (hold) on that measure. Two things will happen, you should get the scale appear so you can check what you should have done and the play button will appear within that measure for you to start play again from there.

If you are having problems, here are some ideas:
- create a separate song with just the chords or progressions you are having problems with
- use the loop facility to practice a specific section
- slow the tempo down sufficiently so you can get through completely many times without making mistakes. It sounds like you are practicing too fast for what you can remember of the scales on certain measures (remember you are practicing, not performing, so practicing slower can help develop your memory and you have more time to check the scales you see)

I hope this helps. Happy practicing!
:)