Even in fairly high profile scenarios, producing a realistic midi mockup of sampled instrument is nowadays a very helpful skill. It's not always possible to arrange recordings with real musicians, and at the same time we as composers want to showcase what we can do in the best way possible, and our clients will rightfully ask for the best quality despite the potential lack of budget. A wonderfully crafted piece of music can easily fall apart without proper knowledge of sample manipulation in this sense. Beside being a composer myself, I had the luck of working for years in studios that specialized in midi productions and sample library programming: I can teach you the software I write with (Cubase) and, more in general, how to get the best results out of your sample libraries, by manipulating them inside of Kontatk/Sine/Spitfire engine, or by advicing you on how to proper postproduce it. We can cover every stage of production, up to the basis of mixing and mastering.