<genuinely amazed at the notion that a composer could be constrained as to key>!
We got tailz waggin dogz here or what?
I am just old fashioned, however, and a creature of other genres, Barnelby. Your piece sounds sonically good to me, but I can't quite locate the bit that I would hum afterwards, or describe to someone else along the lines of 'you know, the one that goes x/the one with the y'...etc. Other rules apply, I dare say
