I have heard bits and pieces of a breeding project whose goal is to design a roo that can be kept in the city. They are breeding for a mute rooster. I don't know what breed it is in, but they've almost accomplished it in just a few generations.
They select their lowest(volume wise) and quietest roo and breed it to the most least "talkative" hen. Their F1 and F2 crow so low, it is barely audible. Their F3's weren't old enough to tell, last time I read.
You could do it in any breed you want.. It just takes time and VERY selective breeding.. You have to have the time to "listen" to your chickens alot, because selection is based on "voice".
Just thought everyone may be interested to know, and maybe take on a "silent strain" in their breed of choice, for those unfortunate people who can't have roos because of noise.
-Kim