I've got a few howlers. Singers, talkers, trillers, too!
Hammie will go down into the basement, where it's dark & spooky, and growl at himself. It sounds like he's asking questions. He gets really loud, and it's just him down there! I think Hammie just likes to hear himself talk, because he really gets into it and sort of has his own language.
Snickers, at nighttime before he comes up to bed with me... will be downstairs all alone & he will sing. It's a really pretty, trilling sound, high pitched and sing-songy. He does it so excessively that sometimes I have to get up & peek my head down the stairwell and call for him til he comes running!
And Dusty, she takes the little birdie toys around the house in her mouth, and makes grunting growly noises. Weird, deep noise that sounds odd coming from such a tiny, pretty, sweet little cat. We think she's proud cuz she "killed the birdie" so she's showing off to the other cats!