I'm with LH.
My Dog, Barney the wonder Dog, sings/howls along when I play the Blues...Memphis Minnie songs particularly....although he has joined in at times with other Blues numbers. I don't think he enjoys Folk as he never bothers then!
I think he is just being a part of it....
Or maybe he is telling me to shut up :>+...either way...He's communicating and I love it.
I used to have a Sheltie that Howled along with the Theme Music from a British Soap my Mum watched called Crossroads. No matter where he was he would fly to the front of the TV and sit there Howling along....it never failed to make us laugh.
Blessings
Jude