There are a couple videos on YouTube featuring dogs singing along with bagpipes. This video is the main one and has a black lab singing (howling) while the dog's owner plays the bagpipes. Apparently the dog sings all the time according to the caption of the video. There is a second video featuring two dogs side by side  with one singing (howling) to bagpipes as well. In the second video the black dog can't figure out why the brown dog is howling and tries to nip him to make him stop. The black dog just seems mildly annoyed by the bagpipes instead.

Check out the dog singing to bagpipes below or click over and view it on the host site (and see the second video).

Source: YouTube