PhilGood said:
So a ribbon mic might be a good choice?
probably about the best choice for fiddle, imo. these are two instruments where the modern cheap chinese condenser with stridently hyped high end frequency bumps *really* work against you.
i totally agree with the folks above--depending on the quailty/timbre of the instruments in question and the technique of the player, these will probably be about the most harsh/shrill instruments you'll ever record. and the less adept the player (and to an extent, lesser quality of the instrument), the more shrill/harsh it'll be. i've heard some great fiddle players with remarkably smooth tone and technique, so a lot (most?) of it lays in their hands.
one of the most important things when recording fiddle is to get the mic up above the instrument and backed off a bit (couple feet or so)--this is where an omni comes in handy. unfortunately (or fortunately, depending on your room) this also means that you're gonna be capturing a good bit of the room. the other thing to keep in mind is that fiddle players usually bounce around a bit when playing, so an omni a few feet above helps mitigate that. and much like drums, walk around the room and find a spot where the fiddle sounds really good and stick a mic right there. this could be your secret weapon.
if the fiddle player has a live rig (attached mini-condenser, under-saddle pickup, etc), take a track of that too. it might actually sound better than what you can get with a mic in the room, might fit in with the sound of the band better, etc.
banjos are usually pretty freaking loud. i'd put a single mic (or a coincident pair) a couple feet in front and adjust the position until you're getting what you want to hear. in short, just mic it a lot like you would a very powerful
acoustic guitar (HD28V, D45, etc).
in terms of mixing, you just want to get them to fit in with the rest of the band, so make sure everything lives in the same acoustic space. and a lot of times "fitting in" requires judicious use of eq and compression. also never underestimate the power of using delay and/or a touch of chorus on the fiddle--that can really fatten it up, and a subtle amount of a nice dark reverb can really help out with the strident highs on both.
cheers,
wade