I consider it a round if the whole song is sung through repeatedly by each group or person doing a part. I think of canons as being part singing but not necessarily repeated. I have no idea what the "true" definition is supposed to be.

You might check around in places like Eastern Mountain Sports for a book and tape called "Hiking A Round". I'm not sure where my copy of the book is, but the tape has copyright 1996 Robert Ellinwood. One of the few tapes of rounds I know of...

When I teach a round (to children) we start by using a familiar one, like "Row Row Row Your Boat", to warm them up and get them used to the signals I used for each group to come in.

New rounds get taught line by line, then sung as a group, three or four times at least, and then we sing it as a two, or at most four, part round, until it's firmly in the class's mind. With older kids who have more singing experience it's easier, and we can do an elaborate eight part round earlier on, but even they need to go through the song several times to get the tune safely into their heads.

It takes a fairly good group to get away with doing "A Tuneful Song", where each person starts individually, but it's a great funny song to reward a lot of hard work.

What rounds will you be teaching?