and running water, Pearl Jam and Indigo Girls set them off. Never in time with the music really but they do rise an fall with volume.

My dog (now deceased) used to sit listening to me play guitar. Well, i was working on an instrumental guitar project where each song was meant to evoke some famous player.
On one song, called Saturated (tribute to Satriani), i started with a feedback note before i did a two hand tapping opening. The dog always howled to that feedback note.
At the end of the opening, i let a different note feedback and the dog would howl again. Except, he would howl a different pitch.
Don't get me wrong; he wasn't howling in exact pitch, but he did howl two different pitches when the two different notes were feeding back.
Well, when i finally recorded it, i left in the room with me so his howl can be heard on the CD!
I gave him vocal credit on the CD jacket. Yep, the dog got vocal credit on an instrumental album!