I just posted this on another thread:
I think the amount of crowing generally has to do with the individual rooster personality. My BO roo and my RIR rooster crowed minimally.
Also, my hens and roos all free-range all over the farm every day, so they're often too busy doing "stuff" to spend a lot of time crowing. IMHO, the happier the bird and the more space they have and the more they tire themselves out free-ranging, the less they crow. Also, I generally keep few roos which may keep them from feeling competitive with other roos and thus crowing more.
Others may have other opinions on this, but I think free-ranging keep them quieter.