Piano, upright bass, drums, sax and trumpet.
Any recommendation what mic pair I should use?
What mics do you have?
Capturing horns and drums will be easy. Getting the bass properly balanced will probably be the biggest challenge.
For a session like this, the bass player really should not need an amp (I play double bass, btw). If the he is a weak player and the drummer is loud, he might want one...
I'd start with a pair of omnis, personally (spaced around 2-3 feet or better yet use baffled omnis). Think about how you want things to appear in the stereo image and position the musicians around the mics. Listen back and move the musicians to adjust balance. When you get it right, make sure no one moves around. Make sure the bass player does not fiddle with the volume knob on the amp if he is using one - he could throw off his balance.
Important - Listen to each instrument individually as well. You have to get your desired balance between direct sound and room sound for each instrument as well as the correct balance between musicians. If you can't get enough room sound out, switch to cardioid or something - but as a last resort. Omnis will probably sound better. Room sound is ok for jazz. Remember to listen in mono too and see if the spaced omnis are really having comb filtering issues. Adjust them slightly to reduce it.
I'd probably put the bass and drums next to each other in the middle, put the drums a couple feet behind the bass (put some more distance between the drums and mics for balance). Horns can be on the other side of the mics facing the drums and bass. Play around with spreading the musicians out more until it sounds right. Don't get too close to the mics.
Do it right and you will end up with a recording that will sound 1000 times better than individually mic'ing everyone.
