After joining famed independent label A&M Records in 1976, he rose to Senior Vice President and Head of East Coast Operations. Known for his gregarious management style and his ear for emerging talent, he was instrumental in the development of the careers of Suzanne Vega, Joan Armitrading, The Police, Squeeze, and Supertramp, among many others.
Leon also served as a Vice President of the Rock and Roll Hall of Fame Foundation, the Head of International for EMI Records Group, and President of independent label Hybrid Records.
After marrying Dart in 1996, he was often seen by her side at gala events around the world, embracing the role of being, as he often called himself, “Mr. Dart” (he even changed his email name to “mistadart”).
Dart founded 42 West in 2004 after rising to prominence as President at PMK. Her clients included Tom Hanks, Martin Scorsesee, Francis Ford Coppola, Nicole Kidman, Darren Aronofsky, and Meryl Streep. She oversaw the sale of 42 West, a company she built from two initial employees into one of the biggest PR businesses in Hollywood, to Dolphin Entertainment in 2017, and she retired from the business in 2021.
In addition to Dart, Leon is survived by his two sons, noted filmmaker Adam Leon (Gimme The Loot, Tramps) and Matthew Leon, currently an employee in the CAA music department.