Leon was instrumental in launching the careers of many recording artists including The Ramones and Blondie. Active in pop music production from 1974–1998, Leon has focused on classical composition, orchestration, arrangement and recording from 1998 to the present.His work appears on many classical recordings with artists including Luciano Pavarotti, Andreas Scholl, Sir James Galway, Joshua Bell, The Royal Philharmonic Orchestra and the London Symphony Orchestra.

Leon has recently turned to work combining audio and visual imagery. Recently he has completed work as a producer and musical director/composer of the PBS broadcast "Quest beyond The Stars" which commenced broadcasting in June 2012 and the Discovery Network broadcast "Orbit:Journey to the Moon" which was viewed on the 40th anniversary of the Apollo Moon Landing. He is also the audio producer and musical director of the PBS broadcast "Bell’aria: Live From Las Vegas".

In 2011 Leon completed the Sony Classical recording of "Midwinter's Eve: Music For Christmas" featuring his orchestrations and arrangements of Christmas music performed by The London Chamber Orchestra conducted by Christopher Warren-Green.