This app was mentioned in 1 comment, with an average of 1.00 upvote
https://play.google.com/store/apps/details?id=appinventor.ai_smathieson.AudioLooper&hl=en this is the one my husband found.
It's not a pretty app, but it does the job! The only thing we can't figure out is how to delete the ones you don't want any more. Time of the loop will depend on how fast you sing. My husband I think has put it on for 200 times (almost 4 hours lol) a few times just to get us through the night. Works a treat! Best of luck <3