I'm now working (very slowly) on a large orchestral piece. As I don't want to use anything but free software, I'm having problems to get a decent sound. It seems to me that the only solution for many instruments is using a soundfont player. I have used them before, but not too much. Do you know wich one is best? Or are all them more or less the same?
Since you are looking for free, the .sf2 player that I can recommend is 'SFZ Sample Player':
http://www.project5.com/products/instruments/sfz_player/default.asp
It gets the job done and works works just fine in OMPT.
In "pay-for" products you usually have more options to adjust the envelope, volume, velocities and generally fine tune the instrument.
This is the best free sf player, but there are some soundfonts with modulated resonance or something, and SFZ can't play them correctly, you can hear something like bird tweet. I have a bunch of these, one of them called molecula.sf2 if someone interested.
But there is VSTSynthFont. It is capable of loading SF2 and DLS banks and I don't know of any other VST which can load DLS, but it can be buggy on certain systems. So it's good to have them both