This really is an interesting topic. I haven't taken a lot of courses on music or anything, but I have read some articles dealing with the relationship of music's effect on humans, but also, on plants. Now I know that plants are definitely a long way from being even related to dogs, but hear me out. When scientists separated plants into two different labs and blasted two different types of music into the areas where plants were being grown, they found that the music being played had a direct influence to the growth and health of the plant. Plant's receiving heavy metal/ hardcore rock music tended to suffer, while classical music seemed to stimulate plant growth. The researchers concluded that somehow plants were able to detect the mood of the music being played through vibrations of sound waves being played in the room, rather than the typical "hearing" senses that animals like humans have developed over millions of years. My overall point for this, is that if plants are able to detect the mood of music through sound waves, then I guarantee you that your dog will be able to as well (obviously because he has hearing). In that case, I would suggest putting on some music that you know has a happy mood/rhythm to it so that your dog feels happy while you're there and while you're out running errands.