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

[Pfcs49]

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)