Looking at this video from youtube featuring the amazing Bob McChensey playing the trombone, I can identify two microphones, the Royer R-121 and the old Sony C-37A. I can see both mics in use, would you guys have any idea how they would be mixed and why they have used both?
The reason for using microphones of different types is generally to get the best features of both. Key would be:
In terms of mixing they would both be EQ'ed individually to get the sound the producer wants - this is very subjective, but with two differing microphones you just get more parameters to play with to bring out the sound you want in that venue.
Also have a read of this question on microphone differences.