The II/7b-V-I progression was used at great length by
Bach , who I think may well have pioneered it. It has the advantage of combining the '
secondary dominant chord' with a seventh. Although this discord was
revolutionary at the time, it was soon widely adopted by Baroque composers.
Example: (in the key of C )
II/7b V I
F# A C D -> G B D -> E G C
This is the 2nd This is the root This is the 2nd
inversion of the of the Dominant. inversion (b) of the root.
supertonic chord
with a 7th added.