Originally posted by griphon2
Fm13???????? Who writes this garbage?, but an incompetent.
Extensions beyond a 7th are ALWAYS dominant!!!!!!! Whatever theory you believe. This logic can not be rewritten. I am amazed and astounded by the persons that try. Fm13=Bb7

Definitely adding 2 many extensions on to a chord will change the character of the chord to an inversion of something else. Here's my POV on chord qualities and the acceptable extensions they can go up too: Aug (triad only), Dim. (7), Maj. (9), Min. (11), and Dom. (13).

In Christophs' case the arranger was actually asking for a Fminb13, which would make it Bbmin7