The 'Sellenger's Round' in Playford (1651) is not a completely different tune to that played late in the previous century. If you listen to the chord structure and the general direction of the melody you'll hear that it is a development of the same melody, just a bit fancier. You can play one on top of the other and they'll fit.

'Sellengers Round' also went under the title 'The Beginning of the World' because, according to the 1607 comedy, 'Lingua' (which also calls it 'Sellenger's Round'), it is in effect the dance tune of the universe, being the first tune the planets played, using Venus as
the treble and Saturn as the bass. When the character Common Sense asks why, then, can we not hear it now, Memory replies that "Our ears are so well acquainted with the sound, that we never mark it." This fits in entirely with the renaissance idea of the music of the spheres.

There are numerous settings of 'Sellenger’s Round', including those in the lute books Marsh, c. 1595, TCD MS 408/2, c. 1605, and Margaret Board, c. 1620 and 1635. In 'A short Account of the Minstrels -Volume One', W. Chappell lists settings in 'Lady Neville's Virginal
Book', ‘Music's Handmaid’ of 1678, and in 'Fitzwilliam Virginal Book' (previously called 'Queen Elizabeth's Virginal Book') there is a particularly fine arrangement of 'Sellingers Rownde' - by royal
appointment - by William Byrd (1543-1623).

Chappell says the title may derive from Sir Thomas Sellynger, buried in St. George's Chapel, Windsor before 1475, but he doesn't say why.

There is much evidence of its great popularity. 'Bacchus’ Bountie' (1593) mentions 'Sellengar's Round' being played joyfully by a fiddler for dancers; Middleton's 'Father Hubburd's Tales' (1604) recalls a sad country Christmas because 'Sellenger's Round' was not danced around the Maypole by moonlight; it appears as a round dance in John Playford's 'Dancing Master' (1670); and the ballad, 'The Rural Dance About The May-Pole' (1671), says: "'Begin,' says Hall; 'Aye, aye,' says Mall, 'We'l1 lead up 'Packington’s Pound'; 'No, no,' says Noll, and so says Doll, 'We’ll first have 'Sellenger's Round'.'" It is the given tune for broadside ballads from 1623, including 'The Fair Maid of Islington' (Bagford Collection), 'The merry wooing of Robin and Joan' (Roxburgh Collection) and 'Robin's Courtship' ('Wit Restored', 1658). As ‘The Beginning of the World’ it is mentioned by Thomas Deloney, referring to the times of Henry VIII (which does not mean this is accurate), and by a great host of 16th & 17th century writers, including the playwright Ben Jonson.