"Don't Sit Under the Apple Tree (With Anyone Else but Me)" is a popular song that was made famous by Glenn Miller and by the Andrews Sisters among others.
In this jazzy solo piano version it's arranged for a ballet class "Allegro" exercise and recorded by Peter James on his album "Music for Ballet Class - MORE Songs from the 1940s"
For more info about the album click here: https://bit.ly/3uaJza1