The larger the ensemble, the more combinations of instruments there are to play with. No brainer. Just keep changing or combining sections as the work plays along. A full orchestra is capable of so much variety of color that do-re-mi can sound fresh and vital. However, the fewer instruments you have, the harder it is to give the work the musical variety that’s necessary to hold an audiences’ attention and interest. Literally, you have fewer colors to work with. Kind of like taking away a large quantity of your paints from you paint box. The real challenge here then is to REALLYknow you instruments.
Whether it’s a string quartet or a typical one horn front line wedding gig band, your knowledge of the individual instruments’ capabilities is critical. You can add a lot of nuance to a chart if you know all of the little subtleties of say, a sax. If your ignorant of the complete instrument you might miss a lot of devices such as sub-tone unison with the bass or slap tongue on 2 & 4 with brushes on snare. And with strings, there’s no limit to the unique techniques and tricks that can be employed.
Just as an accomplished orchestra conductor might take private lessons to learn a stringed instrument to better understand the interpretation of a work, so should the arranger. Get your hands on the ax and see what makes it work. Move those pedals of the harp and understand the limitations of a non-triggered trombone in the lower register. Sit down with the horn player and learn how the mute and hand are used. Learn all of the color possibilities of a drum set and know the difference in sound between sten-in and stem-out of a harmon mute. This will set you apart form the average and get you seats in first class.