John Chalmers MacGregor (March 28, 1903 – March 9, 1973), better known as Chummy MacGregor, a pianist and composer, was Glenn Miller’s pianist from 1936-1942. He composed the songs "Moon Dreams", "It Must Be Jelly ('Cause Jam Don't Shake Like That)", and "Slumber Song".
Read more about Chummy MacGregor: Career, Movie Appearances, Compositions By Chummy MacGregor, Honors