It was written by The Beach Boys’ Bruce Johnston in 1975. Manilow’s version reached #1 on the Billboard Hot 100 chart in January 1976. The original version was recorded by The Captain & Tennille on their 1975 album, Love Will Keep Us Together, who worked with Bruce in the early 1970s with The Beach Boys. The first version I Write the Songs released as a single was by then teen-idol David Cassidy from his 1975 solo album The Higher They Climb, which was also produced by Bruce Johnston. Cassidy’s version reached #11 on the UK Singles Chart in August of that year.
The title has been misunderstood to mean that the singer (or songwriter) “writes the songs”, but Bruce has stated that the “I” in the song is “God”.