As far as Dean can tell, Cas doesn't have a specific favorite type of music. Not that he doesn't like listening to music. Far from it. The angel never turns off the radio. His phone always has some kind of tune playing. He even hums. The thing is, from what Dean has gleaned, Cas hasn't picked a favorite genre. Or even a favorite goddamn day Dean will walk by his room and that light, acoustic-guitar heavy indie shit will be playing and the next the guy will be in there listening to straight up screamo heavy metal – you know, the garbage with nothing but shrieking that you can't understand a word of? There was even this one time, hand of God, dude was listening to fucking Tibetan Monks or some shit. That one had given Dean pause. Not that he doesn't play the stuff Dean likes too, though. The occasional AC/DC song will be heard, and Dean knows he's caught Cas humming Rambling Man on more than one occasion, even if the angel won't admit it.
Sometimes he almost asks Cas why that is. Why he just picks and grabs at everything with a tune. He was especially tempted the day he found the angel cleaning guns in the motel room with Miley-Fucking-Cyrus playing in the background while he nodded his head along to the music amiably. What was Dean supposed to do when an Angel of the Lord was listening to Party in the USA? But every time he started the question, it would die on his tongue. Because of the good days.
Those especially nice days were ones when they were in the car and Metallica would come on. Dean would turn up the volume dial and sing loudly, banging his head to the rhythm while he beat his hands against the steering wheel. Those were the days when he would glance over and see Cas smiling slightly, both corners of his mouth faintly upturned. Those were the days when he was really happy.
Really, Enya is the last straw.
Dean's just out of the shower, drying off his hair, when he hears the steel-drum sound of Orinoco Flow reaching under the bathroom door to stab at his ears. That's when he's had it. He'll put up with Talking Heads and Eminem and, fuck, he even kind of likes Green Day, even if he would never tell Sam that. He likes The Beatles, and there was that one song by Robyn that Charlie played for him that got stuck in his head for days. He's listened to every auto-tuned, shit flinging artist there is on the damn Top 40 station. And if he hears Roar one more time he's gonna shoot someone. But Enya? No. Enya is where he draws the line.
He jams his legs into the pair of jeans he had left sitting on the closed toilet seat and rips the door open, his chest still wet and his hair dripping down his back and face. Cas is sitting at the table with a laptop, mouthing along to the words of the song as he reads. Dean scowls and marches over to the radio, turning if off with a deft flick of his finger. Cas looks up at him curiously, those stupidly blue eyes widening as he raises his eyebrows. Dean throws his arms out to the side in exasperation.
"Enya? For god's sake, Cas, Enya?" he roars. Cas doesn't move, his eyebrows just move up his forehead a little.
"The sound is soothing," he says cautiously. "Her voice is very nice."
"Her voice is not nice! You know, I put up with a lot of shitty music for you, but…" he fades off as Cas's eyebrows sink back down and his eyes lose their gleam, going almost dead.
"I see," he said. "You dislike my music tastes." Oh shit, he just had to put that sad little expression on Cas's face. He just couldn't resist, could he? Dean tried to back track.
"No, not all of your music. You listen to great music!" he tries to sound enthusiastic and fails.
"From now on, you may choose the music," Cas says. He turns his eyes away from Dean and back to the laptop in front of him, any partial expression of happiness gone from his face. Dean's arms lower, followed by his head so it's hanging down against his chest. Fuck. Without a word he flicks his finger again, turning the radio back on in time to hear the last few lines, and then the final fade-out of Orinoco Flow.
A distinctly smug expression takes over Cas's face, although he doesn't turn to look at Dean. Dean scowls again.
"Oh, shut up," he mutters, and then returns to the bathroom. From there he can hear the radio personality announce the next song. Piano keys are played and the first line begins.
"I used to bite my tongue and hold my breath," Dean's hand clenches tight in a fist as Katy Perry's voice carries from beneath the door. He takes a look in the mirror and then breathes in and out slowly.
"For Cas," he says, almost silently. For Cas, you can put up with whatever the hell song comes on next.
Even Enya.