What Pipeline said but I will amplify a just little, and make a suggestion if you only want to use soundfonts (SF2's/SFZ's), and free ones at that.
more explanation about Sforzando, it is NOT a multitimbral VSTi or device. That means, as you now know, each instance of Sforzando can only play one sound at a time no matter how many MIDI channels it receives notes from. BIAB instruments all come into Sforzando (when it is the "default" VSTi) on different MIDI channels with the default MIDI channels being, for example, channel 2 for bass; channel 3 for piano; ... channel 10 for drums.
Now if you want to use a multi-timbral soundfont player there are only a few few left out in the vast WWW wasteland. I won't waste your time and list all the "moldy-goldy" ones that are essentially impossible to find, or send you on wild goose chase to try and find them, it's pointless they aren't around anymore.
Here are TWO, both free that can be easily found. Note, they behave differential from each other
First one is one Pipeline mentioned, Coolsoft’s Virtualmidisynth - it acts like an external MIDI HW module and you would select it as a "MIDI output driver" and the UNCHECK the “use VSTi/DXi synth"” box in the "options - > MIDI/Audio Drivers setup" in BIAB.
Second one, installs and is a VSTi, just like and similar to Sforzando, called "VSTsynthfont" It uses .sf2 files (not .sfz files) but it is a 16 channel multitimbral VSTi soundfont player. Get the free one at middle of page under heading
“VSTSynthFont (1.096 / 2.096) - VST instrument”
Suggestion stick with the 32-bit only version for use at least within BIBA/RB. That suggestion has nothing to do with having JBridge or not having it. It is becasue you won’t find any GM .sf2 over 4GB (not even by half) out there so why hassle with bridging.
http://www.synthfont.com/Downloads.htmlA very good GM soundfont to use, that has grown on me over last 8 months or so, recommend to me by our own John Ford, is one called: “Reality GM 31 MB soundfont.SF2”
However, in a very quick search I could only find one site but that site wanted a donation to download. I know you can find it out here somewhere without paying. But if/when you do find that .sf2 you will probably need a utility called sfark to uncompress it, see
https://musescore.org/en/node/126156If you can't find "“Reality GM 31 MB soundfont.SF2” don't lose sleep - there are other GM soundfont files around that are good.
Good Luck
Larry