Hirschhorn was born in the Bronx and attended the High School of Performing Arts in Manhattan.
After graduating, Hirschhorn became a regular performer on New York's nightclub circuit, both as a solo singer and as a member of the rock & roll band, The Highlighters.
[citation needed] Hirschhorn, along with songwriting partner Al Kasha, did not work on another film until 1970's The Cheyenne Social Club, which was directed by Gene Kelly.
"The Morning After", a song they wrote in a single evening, won them their first Oscar and also topped the Billboard chart.
The pair also worked together on Broadway musicals, receiving Tony Award for Best Original Score nominations for both Copperfield and Seven Brides for Seven Brothers.