I think you would be much better off spending your time listening to recordings and live performanences of solo instrumentalists as well as horn and other like instrument sections within a band and listening to the whole band/orchestra as a whole. Seeing what it is they do and trying to emulate it on your keyboard using it's particular features to use inflection on the different notes using the modulation wheel, after-touch, how you attack the note, being short attack or smooth or legato. This would mean hands on experimenting. The written word here won't help too much. This is all about feeling and inflection. Since it is mostly a feeling kind of thing, if you could learn anything by reading an actual book on the subject, I think that unless you listened and then emulated, it would sound stiff. You would be using the analytical part of your brain which is not into the feeling part of it, but would instead, IMHO hinder what it is that you're wanting to do here instead.
Inflection is what makes the sound whether it's the live acoustic instument or doing it on the keyboard, or a with a vocalist for that matter.
One thing that will make a big difference is noting how the note is attacked. Is is short or long, is it an abrupt attack or is it a smooth attack. Do they hit the note hard, lower the volume instantly and slowly increase the volume adding vibrato. Do they continue at the loud volume or do they let that note get softer? Or, do the get louder and softer more than once on a long note.
Suppose you want to use a clarinet sound. What do your clarinets on your keyboard sound like. What variables can you introduce to change the sound. Plain experimentation is the only way you can find this out.
Do you want to sound like Pete Fountain, Aker Bilk or a classical clarinetist. Each one sounds differently on all playing aspects. To explain this simple thing could take a whole chapter in a book and if you just listened to these examples you would know instantly what it sounded like.
In a nutshell, simply listen and emulate the feeling and inflextion.
I humbly invite you to listen to some of my demos to see what my interpretation of different instruments could be made to sound as realistic as I could manage in different genres using what the keyboards had to offer along with using my tastes and playing abilities:
http://scottlmusic.com/Listen.html Best
Scott
[This message has been edited by Scott Langholff (edited 04-29-2006).]