Joe, Pat gave you some good advice. I will offer another way to accomplish this.

Set your MIDI guitar controller so each string is on a different MIDI channel, lets say 1-6 with 6 being low E. Now set up a VSTi mutli/combo or six different VSTis as follows:
Channel 1 - trumpet
Channel 2 - another trumpet
Channel 3 - tenor sax
Channel 4 - alto sax
Channel 5 - trombone
Channel 6 - Bari sax

Now your high E and B will sound trumpets, G will sound tenor etc.

As for your timbre and other nuance question the answer will depend on what your sound sources are. With some you can not change a thing, these are the least expensive ones, while others, the most costly, offer a lot of nuances, all controlled by MIDI CCs. http://www.samplemodeling.com/en/index.php
are the most realistic solo horn sounds IMHO.

Vintage horns, http://www.bigfishaudio.com/Vintage-Horns
offer the best horn sounds for your initial application. It comes with the free Kontakt player so if you don't have Kontakt you can still use these. They come set up for different groups like JB, Detroit Soul, Menphis soul etc plus you can set up your own groups. I highly recommend these for backing horns.

I hope this helps.

Whenever I get something stuck in the back of my throat, I dislodge it by drinking a beer.
It's called the Heineken Maneuver.

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware