His first arrangements were for the W.S.U. Marching Band of Along Comes Mary a pop song of the time, and concert band transcriptions of the entire Rodeo ballet suite by Copland and the 2nd (scherzo) movement of the Shostakovitch 10th Symphony. He also became interested in jazz and pop arranging in college, having played proms with his high school dance band.

At this time Hearshen started gigging arond the Detroit area, playing and arranging for bands who were doing Motown, and covers for such groups as Blood,Sweat & Tears, and Chicago. During such a gig at the "20 Grand", Ira had to "fill in" or "invent" horn parts for visiting acts such as the "Dramatics", the "O'Jays", or the "Temptations" when they did their shows, because most of the horn parts to the arrangements they carried were missing and the idea was to 'cover' the record. This generally took place at a 1-2 hr. rehearsal about an hour before the show was to begin and was a great opportunity to learn to "think fast" which became a valuable commodity much later.

Hearshen moved to Los Angeles in 1972 and started playing trumpet on casuals and the Latino club scene. He started studying commercial and film music at the Grove School with teachers such as Kim Richmond, Allyn Ferguson, Dick Grove, and Albert Harris. It was thru studying orchestration privately with Harris, that Hearshen got his first opportunity for T.V./Film work. In 1983 Harris reccommended Ira to composer Joe Harnell who needed orchestration help on 2 concurrent series he had going; Cliffhangers and The Incredible Hulk. It was this experience that began Hearshen's career as a film music arranger/orchestrator.

He has steadily worked since as an arranger/orchestrator in Motion Pictures, T.V., and Recordings, for such composers as; Randy Newman, Lalo Schifrin, John Debney, Stanley Clarke, Lee Holdridge and others. His most recent credits include all of the rhythm section arrangements of orchestral film cues in the upcoming release: Undercover Brother, many cues including the final action sequence in The Scorpion King, and the complete orchestral scores for both Rush Hour, Rush Hour 2,as well as orchestrations on A Bug's Life, and Toy Story 2 which included the Sinatra style arrangement of the movie's theme You've Got a Friend in Me by Randy Newman, sung by Robert Goulet. He was also co-orchestrator on Monsters Inc. and was the arranger for both the rhythm section and the orchestra on If I Didn't Have You which won Randy Newman the Oscar for best song at the 2001 Motion Picture Academy Awards.

Most recently, he has arranged the strings for composer/bassist Stanley Clarke's upcoming album.

His works for the Concert Stage include the original compositions Symphony on Themes of John Phillip Sousa, a 45 minute four movement Symphony nominated for the 1997 Pulitzer Prize in music, Divertimento for Band, a Patriotic Overture and Fantasia on the Army Blue commissioned by the U.S. Army Field Band to commemorate the 200th anniversary of the founding of the West Point Military Academy.

It is Hearshen's sincere belief that not only is the art of music arranging not "dead" as some would have us believe, but it is more alive than ever as it is changing with the times in the new world of Electronics, World Music, Computers, the Internet and Multi-Media entertainment.