This Victorian lullaby is a setting to music of Tennyson's poem Sweet and Low by Sir Joseph Barnby. It was first published in 1863.
Barnby (1838-1896) was a composer and conductor, principally of choral music. He wrote one oratorio, Rebekah, and many smaller-scale sacred works including psalms, anthems, motets and 246 hymn tunes. However, it is for Sweet and Low, one of the few secular part-songs that he wrote, that he is best remembered today.
This recording on YouTube is by the top-flight male voice ensemble Pro Cantione Antiqua, conducted by Mark Brown, a beautiful, clear performance.