In B♭ minor, the i–♭VI–♭III–♭VII progression is B♭m – G♭ – D♭ – A♭. The minor four-chord loop: dark but driving. Huge in rock, pop and film.
The library above is set to i–♭VI–♭III–♭VII in B♭ minor. Press Play to hear it with strummed guitar, bass and drums in a rock groove, tap any chord to hear it on its own, or pick another key or a capo.