There's something about country music. You know, beyond the more-beer, she-left-me-again, where's-my-gun stuff. It's some family values in the grasslands, with a little acoustic guitar. It's the patriotism, the drawl and probably the fact that other people don't get it. It just sounds like home.
For example, "Chicken Fried" by the Zac Brown Band:
There's something about opera. Beyond everyone-dies-at-the-end, I-don't-actually-speak-Italian and all the caterwalling. It's the people with grandiose pitch in marvelous costumes, telling a story. It's the wealth of atmosphere, the richness of culture and probably the fact that not everyone gets it. It's the opulence that everyday life lacks.
For example, La Bohème by Pucinni:
There's something about modern electronic/techno music. Beyond the drugged splitting-head-ache, the crazy drunken fans and the heavy rhythm. It's how it can motivate and carry a guy through washing the dishes without quitting, make a country girl dance and turn a group of people into a party. It's funky sounds, weird mixes, the melodic surprises and probably the fact that not everyone gets it.
For example, a song from a French film, Les Choristes, remixed a little hard tech:
Our musical choices explain who we are. What we can't say, music says for us. What kind of music does your character like? Even if it isn't written into the story, could it explain more about them to you as an author? Do you have a special taste in music...or a comment on mine?