Looked up Cowell in the library today–didn’t look systematically or anything, but I flipped through the 11th and 15th symphonies, a brass quintet, and Mosaics something or other and didn’t see anything stranger looking than 7/8; most of it was in 4/4 and tonal or at least not serialist or microtonal or anything. Oh well. Doesn’t seem like it’ll be on audition lists anytime soon. Thanks for bringing it to my attention, though.
Admission…I may be wrong on the Cowell suggestion, or on the other hand, I may be right but nobody else cares…in any case, I maintain that x/10 is fully valid, and saying that it’s not because it might need a textual explanation (as do many other conventions) isn’t a great argument.