I’m trying to decode "Take Five" and so far I have (for my version) it in the key of F with one flat (B-Flat) and the initial phrase (A Section) is based on a D minor which is the natural minor 6th of F. 

The repetitive “walking bass” line I think is A Minor and C Major back to the D Minor. Then the B Section moves to B Flat (Minor?) to C Major to F Major to B Flat Major back to C and it “turns around” a few times before ending up at A Major 7th as the tension chord and then back to the beginning. 

In Roman Numeral Notation this sequence (I think) is 6m mainly for the A section, then the B section with the B flat chord is the perfect 4th of F, the C is the perfect 5th of F, then to the 1 F major and back to the 4 for B flat. 

Am I even in the ball park for this? I’m hoping somebody can decode Take Five for me and explain why these chord changes seem to be unique when compared with many of the I ii V(7) sequences of many jazz songs.