Einar Aaron Swan, born Einar (Eino) William Swan on March 20, 1903, in Fitchburg, Massachusetts, was an American musician, arranger, and composer renowned for his contributions to the big band, swing, and jazz genres. Swan was the second of nine children born to Finnish immigrant parents. His father, an amateur musician, inspired Swan's early interest in music, and by his teens, Swan was proficient in playing the violin, clarinet, saxophone, and piano.

Swan's musical journey began in earnest at the age of 16 when he formed his own dance band, Swanie's Serenaders, which toured Massachusetts. His career took a significant turn in 1924 when he joined Sam Lanin's orchestra at New York's Roseland Ballroom, where he collaborated with notable musicians and began composing and arranging music. He later joined Vincent Lopez's band, touring England and contributing to the release of "Trail of Dreams."

In 1931, Swan wrote the song "When Your Lover Has Gone," featured in the film "Blonde Crazy" and later covered by legendary artists such as Louis Armstrong and Frank Sinatra. Swan also composed "In the Middle of a Dream" in 1939, recorded by Glenn Miller.

Swan's personal life saw him marrying Ann "Billie" Kaufman in 1925, converting to Judaism, and changing his middle name to Aaron. The couple had two children, Pearl and Donald. Tragically, Swan's life was cut short when he died of a cerebral hemorrhage on August 8, 1940, in Greenwood Lake, New York, at the age of 37. Despite his brief life, Swan left an indelible mark on the jazz and swing music scenes.