If You Leave Me Now

Peter Cetera wrote and sang If You Leave Me Now, which came out as a single on 30 July 1976 from Chicago X. He composed it on guitar around the time he wrote Wishing You Were Here. The song nearly missed the album. Cetera recalled that it was recorded live, with Guercio on acoustic guitar, Kath on bass, Lamm on piano and Seraphine on drums, after which his vocal was done over and Kath overdubbed electric guitar. Guercio had played the guitar on the demo, expecting Kath to replace it, but the band kept his part. Parazaider said he heard it on the radio while cleaning his pool and thought it sounded like McCartney.

It topped the Hot 100 on 23 October 1976 for two weeks, and stayed at number one in the UK for three weeks. It won the Grammy for Best Pop Vocal Performance by a Duo, Group or Chorus, and another for Best Arrangement Accompanying Vocalist(s), for arranger Jimmie Haskell and Guercio. It was also nominated for Record of the Year. Billboard writers noted that the song pivots around a French horn riff that moves between two notes.