The song was originally written as a prelude to the song "The River of Dreams" in the style of a monophonicGregorian chant. Joel had written English words in the chant describing a man who had lost his faith, and had then had the words translated into Latin.[1] He changed his mind upon hearing the recording, and incorporated it into the song "River of Dreams". He later removed the interlude from the final studio version of "River of Dreams", and instead wrote lyrics to the melody that reflected his sentiment toward Alexa Ray, who was a young child at the time of writing. The version of "River of Dreams" incorporating "Lullaby" appeared as an alternate version on the box set My Lives, and on An Evening of Questions and Answers...& a Little Music.
In 2004, it was announced that Joel had agreed to write two children's books for Scholastic, the U.S. publisher. The first book was titled Goodnight, My Angel (A Lullaby) and is a picture book based on the song and illustrated by Yvonne Gilbert. "Reassuring children that they are not alone or could be abandoned is very important for their well-being," Joel said in a statement in 2004. The second book was titled New York State of Mind and illustrated by Izak.
In 2014, X Factor UK finalist Daniel Evans recorded an emotional version on YouTube and it appeared as the final song from his best of album, Emotions.
In 2018, Andreas Scholl recorded the song with pianist Tamar Halperin on the album The Family Songbook (Berlin Classics).
