Unusual progression · Rules

Flags a chord connection that is not among Piston's usual ones (and I → II with II in root position). It is not an error: it is a pointer.

Unusual progression: Flags a chord connection that is not among Piston's usual ones (and I → II with II in root position). It is not an error: it is a pointer. (Piston, ch. 3, pp. 21–22; ch. 4, p. 45)