"What makes a round?" a round is a song in parts, each part of which harmonizes with the others. I have a friend who studied rounds in a workshop, and she told me the way to compose a round is to select a scale, then omit the 4th and 7th notes of the scale when composing your melody.

In all rounds I have sung, each set of singers waits out the same number of measures before beginning the song. Thus, a six-measure round has three parts, each two measures long.

It makes the round more interesting if one part is singing eighth notes while another is singing halves or quarters, although there are many interesting old rounds consisting mostly of long notes.

Here are the words to a sophisticated round from the 1600's which we enjoy. Sorry that I don't have a way to give you the tune.

Seven cities of Greece, 'tis said/Claimed Homer's birth when he was dead/Through which, alive, he begged his bread.