I engage in a school project where kids are playing and singing excerpts of Mozart's "Magic Flute". I was asked if I could do some additional orchestra tracks and I happily do.
I found that rendering sounds that should fit into a live performance demand some extra thoughts:
1. The rendering should be very dry because the sounds will be played through speakers and then be reverbed through the actual room. If the rendering would be "pleasing" from the start then it would come out muddy and not very helpful for the people that want to sing along with it.
2. Therefore the rendering itself has to be done quite carefully. No room to hide anything
3. The instruments should be ordered spatially, but how should that be done without reverb? I used a combination of delays, EQ's and early reflections for this.
4. Since school kids sing this, it has to be transposed, fast pieces slower, slow pieces faster than normal, and rhythmically relatively straight forward.
Here you hear the aria "Dies Bildnis ist bezaubernd schoen". This is the first rendering I entirely played in with keyboard ... every voice in realtime, and with HEAVY modwheeling, so it is not perfect - but lively, hehe . First you hear the dry orchestra only, and then, for fun, a wet version with a solo flute.
EDIT: If you feel like you can happily sing along with it It's fun!!!