learned from Rebekka Goldsmith www.RebekkaGoldsmith.com
Group stands in a circle (this requires a fairly large group, maybe at least 10 people).
Leader creates a simple repeating phrase and sings it to the next person.
That person sings it to their next person and then continues to sing that phrase. Each person continues to sing the phrase as it gets passed from person to person.
When the phrase is part-way around the circle, the Leader creates a new phrase that interlocks and/or harmonizes with the first part. Leader sings it to the next person who then changes to the new part and passes it to the next person who shifts to that new part and continues it around the circle.
Leader continues to add new parts so that there are several parts being sung at once by the circle.
The leader can be conscious of shifting meter and tonality so that the harmonies and overall sound shift and change as new melodies are added, and old melodies fall away.