HARMONIC PROGRESSION - The way in which chords are selected to succeed each other in a piece of music.

CIRCLE PROGRESSIONS - Direction and Drive toward a goal - The Tonic!

Descending Fifths -   I     IV   viio    iii     vi     ii     V     I    - moving toward a Perfect Authentic Cadence.

(Reminder:  the   Viio6  -  I    can be interchanged with V  -   I  as they share the same pitches...

Ascending Fourths from a Deceptive Cadence     -    vi   ii   V   I  

Ascending Fifths, Ascending Seconds, Ascending Fourths     -     I    IV    V    I    (This progression will switch the circle).

The Music of the Classical Period depended heavily on standard chord progressions for its structure.