"Old MacDonald Had a Farm" (sometimes shortened to Old MacDonald) is a traditional children's song and nursery rhyme about a farmer and the various animals he keeps. Each verse of the song changes the name of the animal and its respective noise. For example, if the verse uses a cow as the animal, then "moo" would be used as the animal's sound. In many versions, the song is cumulative, with the animal sounds from all the earlier verses added to each subsequent verse. The song was probably written by Thomas d'Urfey for an opera in 1706, before existing as a folk song in Britain, Ireland and North America for hundreds of years in various forms then finally being standardised in the twentieth century. It has a Roud Folk Song Index number of 745. The lyrics to the standard version begin as follows, with the animal sound changing with each verse: History Thomas d'Urfey The earliest variant of the song is "In the Fields in Frost and Snow" from a 1706 opera called The Kingdom of the Birds or Wonders of the Sun written by the English writer and composer Thomas d'Urfey. This version begins:In the Fields in Frost and Snows, Watching late and early; There I keep my Father's Cows, There I Milk 'em Yearly: Booing here, Booing there, Here a Boo, there a Boo, every where a Boo, We defy all Care and Strife, In a Charming Country-Life.It is unknown whether this was the origin of the song, or if his version of the song was based on a traditional song already in existence. Like modern versions, the animals change from verse to verse and the rhythm is very similar, but it uses a different minor key melody. D'Urfey's opera was largely unsuccessful, but the song was recycled, being expanded and printed in d'Urfey's own Wit and Mirth, or Pills to Purge Melancholy, vol. 2 (1719) and appearing in several operas throughout the eighteenth century such as John Gay and Johann Christoph Pepusch's Polly (1729). It also appeared on song sheets for decades, so it was presumably popular among ordinary English people in the eighteenth century whether it originated from the opera or not. Traditional English versions Several versions were collected in England in around the turn of the twentieth century by folklorists, such as one called "The Farmyard Song" taken from a John Lloyd of Manchester in the