Progression Chart shows the harmonic scales and Nashville
Numbers for all major and minor keys.
The Nashville Numbers around the
inside of each circle remain constant while the chords around the outside
change according to the specific key.
Chord Progression Chart will save you tons of time and tedious effort,
especially when you want to get creative with variant chords and
modulations to other keys.
For complete explanations of
harmonic scales and Nashville Numbers, consult
How Music REALLY Works!,
2nd Edition, especially Chapter 6, which covers these topics in detail, with many examples.