The harmonies of a round result when different voices begin and end the melody at different times. If the voices begin at different times yet end together on a final chord, the song is called a canon. Rounds and canons were very popular in the 17th and 18th centuries, and in a variety of settings--from William Billings's sacred "When Jesus Wept" to Henry Purcell's bawdy "I Gave Her Cakes." They can be as long as a full verse of a song, or as short as 2 or 3 phrases. Colonial Revelers begins each of their concerts with the round "Now We Are Met," composed by Samuel Webbe (1740-1816), as heard in the video above.
The easiest way to learn a round is to sing one part over and over until you've got it, then move on to the 2nd part, then the 3rd. You might, for instance, sing only "Row, row, row your boat," over and over, while your friends sing all the way through the round. Next time you'd sing "Gently down the stream," until you're sure of those notes. Then "Merrily, merrily, merrily, merrily," and so forth. Eventually, you've got the whole melody.
Some of Colonial Revelers' favorite rounds and canons:
Now We Are Met (Webbe, late 18th century)
Sweet Sir Walter (Purcell, 1733)
I Gave Her Cakes (Purcell, 1731)
He That Will an Alehouse Keep (Ravenscroft, 1611)
Banberry Ale (Ravenscroft, 1609)
Christchurch Bells (Aldrich, 1673)
The Sports of May (Warren, 1775)
When Jesus Wept (Billings, 1770)
Canon (Billings, 1770)
You can hear these rounds on either the Down Among the Deadmen or Revelry, Reflection & Revolution CDs.
As ever, your humble servants,