Having come to the conclusion that it would have been impossible for me alone to understand how and what to do to make my tracks sound better, I decided to ask someone qualified to guide me through actual lessons on audio, virtual orchestration, mixing, and mastering.
Well, after a couple of rejections from people who work specifically in the field of creating demos for virtual library manufacturers, I turned to Simone Renzi, the founder of this site, and he, much to my surprise, accepted.
I am writing this in the Pro Tools section because the reference software we are working with is indeed Pro Tools; so far we have had three meetings and I have learned many things, even though we are only at the beginning and the topics are not easy at all.
It's a bit like composition: the subject is still quite "craft-based" and requires a 1-on-1 relationship to be guided step by step, so I believe I have made the right choice.
I thank Simone for his enthusiasm and expertise; I hope to be a good student....