“Once Upon a Time” is from the 2004 Broadway musical Brooklyn by Mark Schoenfeld and Barri McPherson. The story follows a group of five homeless musicians in New York City who put on a play about a singer named Brooklyn under the Brooklyn Bridge in New York. The original production ran for 284 performances.
The track, which features Eden Espinosa in the lead role, begins in Bb and shifts up a half step to B at 2:14.