Malcolm! There is virtually nothing out there about Hazel Wrigley's or Willie Johnson's approach to back-up guitar - apart from the fact the Willie was inspired by Django. Now, Django's rhythm style was straight ahead 4 beats to the bar - very different than Hazel's approach. No, there is a book out there waiting to be written showing how the Shetlander's adapted Django's rhythm playing to suit backing fiddle tunes.