"Got A New Lease On Life" from In Person played in the background

i'm currently watching this movie and just got to the roller skating bit, but i noticed something interesting this time 'round:

just before the number begins, there's a bit of "got a new lease on life" from in person being played in the distance as fred and ginger talk. on my dvd copy (from the tcm astaire and rogers collection, for what it's worth), it begins at 01:09:45 and ends at 01:10:15, with the piano introduction to "let's call the whole thing off".

now this technically isn't too strange, since in person was released two years prior to shall we dance, but my question is...why is it here? i was under the impression that all the music for this movie was written by gershwin, and "got a new lease on life" was seemingly written by oscar levant. maybe it was included to fulfill a thematic purpose, showing that their relationship has solidified thanks to a happy day in the park (since the song is about getting a "new lease on life" through falling in love). either way it's strange to hear a song from another movie, particularly a very little-known oscar levant song. (unless it was actually written by gershwin?!)

any thoughts?

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(only Kirk could have his brain seared and escape injury)

"i don't like salad"