Renardo pre-defines Roman numeral chord constants I–VII as PGroups for quick chord progressions

Renardo’s Chords.py defines I through VII and I7 through VII7 as PGroup constants representing triads and seventh chords built on each scale degree. For example, I = PGroup(0, 2, 4) is the tonic triad in root position. Seventh chords add an additional degree: I7 = PGroup(0, 2, 4, 6). Being PGroups, they fire as simultaneous chords and support arithmetic: I + 7 transposes the entire chord up 7 scale degrees. Combined with var(), this allows chord progressions to be written compactly without spelling out every note.

Examples

p1 >> pluck([I, IV, V, I], dur=4)   # I–IV–V–I progression, 4 beats each
p1 >> pluck([I7, V7, I], dur=[4, 4, 8])  # jazz ii–V–I with rhythmic variety

Assessment

What notes (as scale degrees) does IV contain? Write a 12-bar blues progression as a Renardo player line using the Roman numeral constants and var().