How's your roo today? I would take dlhunicorn's advice - she is VERY VERY knowledgeable about all things chicken/illness related!!!
Hope he pulls through for you!
Well, if it was me, I'd start him on Tylan water soluble antibiotic. It's excellent for respiratory ilnesses. But, you can't get it at most stores. I ordered mine online - and, it's expensive. But, when I have one that starts sneezing, I watch it for a few days to see if it'll get over it on...
It seems odd that he's not sneezing, and only makes this sound after he crows. Can you look in his mouth and see if you can identify any irritation (redness) or sores? Should look like this:
If it's more red, there's something in there irritating him.
Gosh, it's so hard to know without hearing it. Do you by ANY chance have a digital camera that records videos with sound? I have a pretty inexpensive one that will take a short (I think 15 second) video and it records sound with it. If you could possibly do that, it would be very helpful.