Lullaby is a song by Johannes Brahms for voice and piano. It was first published in 1868 as part of his Op. 49, No. 4. The song is also known as Wiegenlied, which means cradle song in German. The song is in the key of E-flat major and has a tempo of 88 beats per minute. The song uses a simple chord progression of I-V-vi-IV throughout. The song is based on a folk poem that Brahms adapted for his friend Bertha Faber, who had a newborn son. The song is about a mother singing to her child to sleep. The song was very popular and has been arranged for various instruments and ensembles. The song was also used as the second theme of the first movement of Brahms's Second Symphony.