It’s a bit disappointing, the quantity of relevant data yielded by my research on music therapy in pets. There hasn’t been a whole lot of exploration done, and the studies don’t seem particularly well constructed. For example, special pieces have been written for both domestic cats and tamarin monkeys to explore the effect on their mood, to the extent that mood can be calculated by an outside observer. Both studies yielded positive results; however, both sets of materials contained clips mimicking the communication sounds emitted by those animals. Is that still “music”, or is it more like background chords to accompany a voiceover? In tests of species-centric melodies, the instrumental component was never isolated from the animals’ vocal samples, so how can we fairly judge the impact of the composite piece? Put another way: when a pet cat hears purring in his playlist, does the background music matter at all, or does he merely perceive language that he knows as the output of a happy cat?
As in humans, response to music can be divided into two main branches—(1) the feelings evoked by a particular song the first time or two one is exposed to it, and (2) the emotions experienced when hearing a song that one has linked with remembered events or scenarios. The former hasn’t made a great showing in well-constructed studies of dogs and cats, but the latter still has a lot of potential. We know that our pets can learn and memorize a seemingly limitless variety of sound cues. They have an eerie ability to tell the future based on complicated sequences of sound: the subtle contrast between different jacket zippers and keyrings tells your dog whether he can expect to go out for a ride. Clicker training, an enormously successful behavioral technique, is based on a single sound just a tenth of a second long. Our pets’ response to sound is extremely sophisticated; there’s no reason to think a dog or cat of average intelligence couldn’t be trained to display a particular behavior in response to a specific song recording.
To a certain extent, some animals of some species have demonstrated a somewhat consistent initial reaction (positive or negative) to musical pieces created for human listeners. But you shouldn’t count on Mozart to do the heavy lifting for an anxious dog; any positive effects won’t persist without deliberate training. Cat owners might be better off choosing “cat music” (available online—but do your research to find a reliable source). Within those boundaries, the sky’s the limit. Teach your pet to sit nicely on his rug when he hears the magic song, or enter his crate, or just overall dial it down. Train him to “like” music, even if he can’t hear it the same way you do. Then release your findings to the community, because there’s not a lot of information out there. You are the cutting-edge researcher, because the ones who came before you either failed to complete the job or didn’t see a profit in it. Gentle reader, I thank you in advance.

Dr M.S. Regan