Is there an accepted convention for the order in which members of the pitched percussion family should appear in a score, please; and unpitched (below them) for that matter?
I’m afraid I don’t have the various orchestration reference texts like Adler et al. at my fingertips here in my home office, but I think that’s probably your best bet. Check Adler, check Stiller, perhaps check the new Solomon book on writing for percussion.
My recollection is that there isn’t considered to be a specific “correct” order for unpitched percussion instruments. You’re advised to group them in the score by player, if possible, and to put the timpani and pitched percussion before the unpitched percussion, I believe, but I daresay there are many different conventions in use out there, and almost certainly they vary by composer, historical period, and publisher.
Thanks so much, Daniel!
Neither Adler (4th ed.), Blatter, Forsyth nor Piston seems to advocate any hard and fast rules, as you suppose.
After rushing past the section, ‘The Value of Not Reading This Book’ in Solomon, I found more in his Chapter 3 than anywhere else. I’ll follow what he says - but I’m sure you’re right that I need not be bound by any one set of rules 
.
I may try to go down vertically by pitch!
(Am experimenting with a percussion-only piece.)
Thanks again for jumping in on this on a Saturday night, Daniel.