You think so SC ??

After all he DID try to get Kay to just watch Johnny sing and she playfully nagged him; of course it's true that if he REALLY didn't want to tell her the story then nobody could've made him do it.

Another thing to consider is just the logistical fact that Kay represents US the audience..the only outsider who needs to be let in on family background relevant to the story (such as how Tom Hagen became part of the family). Her introduction to the Corleones is ours as well.

If it hadn't been worked in that Michael told Kay the bandleader story...then where else would it have fit into the film in order for us to know about it?

Apple