the noises are different for different things if its a loud wailing like I WANT ATTENTION NOW then he is calling the females to let them know superstud is in town, and warning the other toms he got there first, if its like yowling and hissing and what i call cat swearing that hum from the back of the throat then he is actually fighting or confronting another tom, i would ask around when you get to know your neighbours if there is a whole tom or female in the close
the tom cat is probably responding to a female in heat near you and is probably fighting with another tom or confronting one you couldnt see, and your cats reaction was just thier individual way of being nosy i live in a cul de sac and quite often hear the males fighting even though all the female cats in this close as far as i know are neutered
Forgot to add - for what it's worth - that although a cat owner for quite a few years, I've not long lived in this suburban house and never encountered tom cats yowling when living in quite isolated countryside, hence what may be an obvious answer for people!
Woken up about 30 mins ago by that very loud (just under open bedroom window) awful yowling that tom cats make, usually at night. My two fast asleep cats both leapt up and raced to the window where one sat passively watching out, whilst the other gazed intently with ears pricked and tail twitching.
What was tom cat's message? Is it part of a mating ritual, calling females to party central or is it a marking territory thing? There were no other males around to start a fight with.
Both cats still on window cill - one curled up sleeping, one looking out with interest!