Actually, now that I am actually sitting down at my board trying to play the progression, I am not even sure if that progression can be considered in Db, because it is coooonstantly changing keys.
I don't agree with that statement.
4hisglory, your explanation above about tritone substitution places this progression squarely within Db. To me, a key change is more obvious. For example, listen to "Ribbon in the Sky", which obviously changes keys twice from Db to D to Eb. One can definitely hear the key change in that song. However, I don't feel like the posted progression has an abrupt key change. Further, it’s OK to play some chords that don’t belong. The spice is what makes music interesting.
This is just my opinion. I may be wrong.
