I'm curious about the process of tracking ensembles, meaning trios, jazz ensembles, folk ensembles, etc. in live recordings, how to prevent bleeding and make every track controlable within the mix, can you give me some tips?
First - don't worry about the bleed. Neigh...EMBRACE the bleed. Capture the ensemble, not the instruments. In this case, the ensemble IS the instrument.
If you really want that last little bit of control, capture the ensemble as an instrument first, then feel free to lightly spot mic each instrument. You can then make minor adjustments in the mix later.
However, if the ensemble is good, they will do their own mixing for you and you don't have to worry about a thing except for capturing the best sound you can.
Seriously, try this just once (if not more)...Throw up as many mics as you'd like on a folk ensemble or jazz combo, etc. BUT, also throw up a quality main stereo pair. Record everything as you normally would, but then, during mixdown, try pulling out everything except the stereo pair. Find what you're "lacking" and put it back in to taste. Subtle is the word of the day for this technique though. Don't go raising all the faders back up to the top or you'll wind up with a mix that resembles more of a rock band than an acoustic ensemble.