Peggy Gordon is a singer/songwriter

Songwriter

A songwriter is an individual who writes both the lyrics and music to a song. Someone who solely writes lyrics may be called a lyricist, and someone who only writes music may be called a composer...

 best known for her role as Peggy in the original 1971 Off-Broadway

Off-Broadway

Off-Broadway theater is a term for a professional venue in New York City with a seating capacity between 100 and 499, and for a specific production of a play, musical or revue that appears in such a venue, and which adheres to related trade union and other contracts...

 cast of Godspell

Godspell

Godspell is a musical by Stephen Schwartz and John-Michael Tebelak. It opened off Broadway on May 17, 1971, and has played in various touring companies and revivals many times since, including a 2011 revival now playing on Broadway...

.

Gordon wrote the music By My Side with fellow CMU

CMU

CMU may stand for a university:*Carnegie Mellon University in Pittsburgh, Pennsylvania, United States*Central Michigan University in Mount Pleasant, Michigan, United States*Canadian Mennonite University in Winnipeg, Manitoba, Canada...

 student Jay Hamburger writing the lyrics. It was the only song that survived the re-scoring of the show by Stephen Schwartz

Stephen Schwartz (composer)

Stephen Lawrence Schwartz is an American musical theatre lyricist and composer. In a career spanning over four decades, Schwartz has written such hit musicals as Godspell , Pippin and Wicked...

. She sang this song in the musical production, with Gilmer McCormick

Gilmer McCormick

Gilmer McCormick is an American actress and singer best known for her performance in the stage and film versions of Godspell in the early 1970s and for her role in the 1984 horror film Silent Night, Deadly Night....

providing harmonic vocals.