"Bye, Bye, Baby (Baby Goodbye)" is a popular song written by Bob Crewe and Bob Gaudio, a member of The Four Seasons whose version of the song made it to No. 12 on the US Billboard Hot 100 in 1965. On the original issue of the single, the title was "Bye Bye Baby"; on The 4 Seasons Entertain You album (and later issues of the song), the name was changed to the longer, more familiar name. The song is about saying goodbye, not because the person is unloved, but rather that another commitment is preventing their relationship.
After a winding seven-bar introduction in B minor, the song settles into a triplet-swing beat and thereafter alternates between two keys, F-sharp major (in the chorus) and A major (in the verse and final chorus), bridging the gap with a five-step chromatic pivot-modulation (D-D♯-E-F-F♯ over the line "She's got me and I'm not free").
A cover of the song by the Bay City Rollers sold a million copies and hit No. 1 on the UK Singles Chart for six weeks from March 1975. It ended the year as the UK's top selling single. The Four Seasons' version is quite sparse in instrumental backing, instead carried by the vocals, while the Bay City Rollers' version is faster and has a fuller backing sound. Played a full tone lower, it includes an eight-bar guitar solo by Eric Faulkner, which is not present in the original.