that goes; iv7 to ♭VII7 to I .
Sounds really bluesy.
By a theoretical reharmonizationtechnique,
Modal Mixture, thebVII7 R, since
the music goes in a major key, borrowed from
the paralell minorscale and therefor it´s allways
a dom7 chord.
Use Modal Mixture for ex. if you want a major song
a little bit darker or vs/.
Modal Mixture R also called Modal Interchange, MI.
(A Berklee Uni. term.)
by Paxom, 2020.