MIDI orchestration can sound wonderful if it’s done properly. But if your orchestrations sound lousy, there are usually good reasons that are easily solved by understanding real orchestras.
If you are emulating real orchestral instruments with MIDI, the whole thing can sound really bad really quickly if you have the instruments playing in a way that’s not they way they normally do. For example, pizzicato (plucking the strings) on a violin can add a sophisticated, percussive effect to your music. But it will sound phony and weird if the pizzicato is too quick. Why? Because the human hand can only pluck a string at a certain maximum tempo; any faster and it will sound unreal, even to those unfamiliar with the technique.
Another problem that is all-too frequent is if the orchestra is improperly panned. Enter “symphony orchestra” into Google Images to find pictures of real symphony orchestras, and you’ll see that there is a somewhat standard way of setting the ensemble up. Try to copy that into your pan settings.
Writing for a real orchestra is not easy – it’s the sort of thing that people study and get degrees for! So if you really want to be good at it, get a good book. You might want to check out texts by Samuel Adler and/or Kent Kennan: they’ve written two of my favourites. Also, Canadian composer Alan Belkin has written a text that he provides for free online at his website. The book is called “Artistic Orchestration,” and the principles you’ll learn regarding writing for a “real” orchestra will be the same principles when writing for MIDI orchestra.
In Belkin’s text, he talks about the “graying” of sound, by which he means doubling or tripling a melody on different instruments. So instead of adding lots of flutes, clarinets, trumpets, etc., to your orchestral melodies as a way of increasing volume, try choosing one instrument and increasing the velocity or track volume. By doing so, you preserve the unique sound of the instrument you’re using.
Of course, you’ll want to find a good book on MIDI orchestration to help you with the technical aspects of MIDI orchestration (“The Guide to MIDI Orchestration” by Paul Gilreath is highly regarded), but my most important piece of advice to you is: MIDI orchestras need to be treated like real ones if you want them to sound real.