The Seal Lullaby by Eric Whitacre is a very impactful and emotional piece that has become widely popular in band programs around the nation as of late. The piece came to fruition when Whitacre was approached by Disney executives and asked to write a piece for their newest movie "The White Seal".
Shortly after Whitacre wrote the piece, however, the movie idea was scrapped. This piece was then left as a standalone choral piece, and later adapted for band.
Whitacre drew his inspiration from he Rudyard Kipling poem entitled The White Seal, which he also used for the lyrics to his choral adaptation. The poem can be found here: http://www.authorama.com/jungle-book-7.html