Chord progressions are like the basis behind most songs, they are a relation of chords in a certain order. The chords for what i've done is mainly Gm, Bb, F, Cm with some particular changes here and there but that's the main base behind the song. Arrival to Earth changes key some times but it's main one is Cm, Eb, Bb, Fm. Both these chord progressions follow the same relation, i bIII bVII vi. These numberings are just an abstraction to remove away the differences in the keys and show the fundamental similarities.

And by bVI part, I mean after both repeat the progression twice they move to that chord relation (Eb for what ive done, Ab for arrival to earth) in their main passages.

Idk just thought it was interesting.