My neighbors have 3 chickens as pets (with possible intention of organic eggs also), 2 of them are male broilers, and one of them is a female of, what I suspect to be, Rhode Island Red; as a result the female is larger than the males; and I suspect the breed diversity to be one of the reasons why they won't mate, as a result no eggs. :(
Regardless, since they were alone from the rest of the world, the roosters didn't learn how to crow naturally, they did it wrong, they didn't even sound chicken; I think I made them learn how to crow
I used my phone to make the roosters crow. That way they responded cause of rivalry, and finally learned how to crow and they're pretty loud now.
One of the 2 males till date (now adults) has not learn't yet how to crow properly, as a result he sounds weird.
So the rooters LEARN how to crow it doesn't appear to come naturally.
But unfortunately, what they also learned is that they should crow at night; and that's cause I'd set the ringtone to rooster crowing in one of my phones and I used to keep near the window.
At night someone used to call me; I don't know who till date, but I was notified about this by my neighbors who complained that the roosters are troubled cause of it; as a result, I moved the location of the phone and changed the ring tone.
What the neighbors didn't tell me was that, their chicken learned to cow at night. Yes -- they'ld randomly start crowing at like 2200, 2300, 0100, 0300.... anytime and for no valid reason!
Another strange behavior was that, a few months ago, the chicken started crowing.
And although slow, it's getting better till date.
People say that it's cause the hen is lacking mates, i.e. they do this when there're no males in the group, and so trying to take over the leadership; this seems to be related to the fact that the roosters were not able to fertilize the hen. Maybe the hen thought the roosters where hens too.