Hi Mark,
You have heard Khachaturian's ballet music; I discovered him 50 years ago through his piano concerto, which I still like.

I don't know as there is much difference between writing for orchestra and midi orchestration, as long as the midi sound is from a print out that could be used by live musicians. The main thing is to be aware of the range of "real" instruments, as well as the differences in sound. The most glaring difference is that midi wind player has to tongue every blasted note, and the brass players, too, though it's not so apparent there, as every note on a separate bow stroke isn't in the string ensemble 1.

The metronome is one thing I haven't figured out, in Composer. Turning it off doesn't affect playback and I don't enter notes from an external midi instrument, at least not now.

I could tell you some of the ideas I got while listening to your improvisation, but I'm not sure it would be of much benefit. I wouldn't worry about things such as beginning with an orchestral statement of the ideas. Beethoven starts his 4th with solo piano and the 3rd movement of his 5th begins with a piano flourish. What I thought, on second hearing, when it came to measure 110 went something like this: A brief statement of this theme would make a good beginning, with strings in upper octave 6, ppp and tremolo, playing sustained notes and the melody by i'm-not-sure--perhaps an English Horn.

Yes, I compose. I started just over 50 years ago, when I studied piano and composition with a jazz man classically trained. He showed a thing I wrote (which should have been called arpeggios in D minor, I suppose) to a concert pianist living in the area and she said it should go a long way toward getting me a scholarship. But I found that I had a thing about manuscript paper, which I still have. I could scarcely read what I'd written and no one else could even begin to make it out, so I spent hours trying to make three or four pages readable. I wrote only two pieces over the next many years. A piece for flute and cello for the wedding of a friend, which the groom's brother and I played on the rim of Canyon de Chelly one hot June morning, and when Bonnie Jo Hunt (the only Native American opera singer that I know of) asked if I would do something for her to use at a dedication, of a cathedral, I believe, I wrote an arrangement of "Simple Gifts" for soprano, piano and flute, of which I am now doing in an extended version for the same group and orchestra. But the labor on these pieces--getting them readable--convinced me of what I had known for years: that I could write nothing of symphonic proportions without having a number of years free to do nothing else. (My handwriting, even my signature, is virtually unreadable, too, I'm told.)

But when I wrote these two pieces, the computer was coming into its own--I had a Kaypro MSDOS machine at the time--and I began, then, to wonder if there would ever be software that would let you use the screen as blank manuscript paper. The computer guy at the college where I was teaching hadn't heard of any, and it wasn't until the mid 90's that I heard there were some being written. I didn't get on-line until 99, or so, and I used the computer for investment purposes and writing, mainly. I did some searches, but found something affordable only a couple of years ago. Since then, I've completed drafts of a couple of symphonies, a couple of piano concertos, and some things for piano and violin and piano. The big problem was getting a score printed. The program I found was quite powerful and easy to use when it came to writing and editing the music, but when I tried to extract the parts for a violin sonata, to send to the people who would perform it, I found there was no way to do it.

I have no .not files yet (I'm still experimenting with/learning how to use Composer). But it does a great job of reading in midi files, and I hope to use it to edit already-complete drafts as well as finish in-process things, and of course write new things. I will put a midi of something up on the Share Your Music site in the next few days.

Back to your piano/orchestra piece. If is to have more than one movement, might it not be a good idea to play around and see if additional musical ideas emerge, that would work with what you already have? Or maybe just plunge in and begin to work out a single movement and leave other decisions for later. In any case, I'll look forward to seeing/hearing what becomes of it.

all best,
mgj