According to the Oxford Music Online, Folia is a:
“A term for a musical framework used during the Baroque period for songs, dances and sets of variations. In the late 17th century a related, alternative form gained popularity and for some time co-existed with the original model.”
Gerbino, Giuseppe, and Alexander Silbiger. “Folia.” Grove Music Online. 2001;
We will begin by studying the harmonic framework of the Folia:
This simple includes several bass clausulae (D-A-D in d minor and C-F in F major as well as a discant clausula moving back to d minor (C#-D). Remember that the # indicates a sharp on the 3rd from the bass and the 6/5 indicates a 6/5/3 chord.
