Yes, Rhythm Changes (key Bb), uses that dim7 a lot....

the second bar can be

| Dm7 C#dim7 | Cm7 F7 |

for that one, I've thought of the C#dim7 as an A7b9/C# .

Then a few bars later (Bar 6), when it comes up again ...

| Eb6 Edim7 | , we have that same chord again (Edim7 is similar to C#dim7 and Bbdim7).
But in this case I think of the Edim7 just like a Eb7b9 (ie no real change of chord).


Have Fun!
Peter Gannon
PG Music Inc.