My Suzuki book 6 student suggested something I hadn’t considered yesterday that was very interesting. La Folia as a 2 part violin canon. It works until the third page when one of the variations becomes 8 bars instead of 16. Instructions:
Player one plays the theme alone. When player one reaches the first variation, player two begins the theme. Both players continue playing as it comes, but player two must defer to the (occasionally new) tempo set by player one.