It’s basically the standard expectation that when my car starts, loud, awesome, 80’s metal will ensue. For the entire duration of the ride.
Jacksonian Demography?
Big difference… you’re supposed to listen to Avril Lavigne.
Xanadu soundtrack on CD.
I win.
I don’t know what to call it, but this happens to me all the time, since I have extremely eclectic musical taste (my husband insists it’s not so much “taste” as it is “complete lack thereof.”)
The only time it REALLY created a problem for me was when I loaded the car full of fourth-grade Girl Scouts and started the car, forgetting that I’d been listening to the soundtrack from Hair.
“SodoMEEEEEEE!, fellatiOHHH!, cunnilingus, pederasty…”
Audiocornholia. Minnie Ripperton so infected me last.
Awwwwww. . .slam fuckin’ DUNK motherfuckers!!!
Quadrophobia
What do I win?
Xanadu movie on VHS.
I win in a related category. 
I have a CD of Finnish folk music I use for this purpose. 
I am a twenty-nine year old single female with eclectic musical tastes. (I own both JCS and Avril Lavigne–as does my mother, which might worry me more.) Like Regallag, the largest possibility is the sudden and ear-shattering attack of the Hair Metal Bands. I’m from New Jersey, I’m expected to own every Bon Jovi album (which I don’t)–but people who think you’re cool will completely reverse their opinion when they discover that the CD in the player is Poison’s Look What the Cat Dragged In.
I get embarrassed about some of my musical soundtracks, too. Mostly because I’m singing along at the top of my lungs, so that’s totally my fault.
Compact Discust (pronounced ‘disgust’, for anyone who can’t read that.)
[Zoolander]
Oh, this is this fantastic band, the Little Kings, I met when I was ice sailing in Finland. And that’s my sherpa, Lap Sang.
[/Zoolander]
I like that better than my suggestion. 
More multipurpose, though in my case the emphasis would be ‘Discomfiture’.
I was thinking about this while driving around at lunch, and it occurred to me that I’m really not terribly concerned about what anyone who might get into my car would think–these are people that know me, and know I’m odd.
It’s other drivers, who stare at me in traffic and might even be able to hear me through the windows, that concern me. What do we call that?
I don’t know what to call it, but I’ve discovered that the only way to deal with it is to go wild. If someone catches you singing along in your car…turn and sing to them! Throw all of your passion into it. Make their day!. If you are playing air guitar, go Pete Townshend on them. Get those windmill strums a rockin’! It’[s the only way to avoid major embarassment and laughter from the other car. Make them slink away, not you.
This also works with opera.
What do you call it when I’m driving up I-95 with 50 Cent cranked, and then when I get to a red light on MLK Blvd. in Baltimore City, I turn it way down, or off?
We need a name for that.
Yes, I know it happened in “Office Space”. I also know it happens to me like 3 days a week.
You’re absolutely brilliant. I now look forward to being stuck in traffic next to some old stuffy stick-in-the-mud who thinks I’m crazy and shouldn’t be allowed on the road. Thank you. Thank you so much.
Trunk, I believe that’s called Whiteguydoesntwannagethisassbeatophobia.
That’s a catchy name, but it’s not really that either.
More like “white guy from the other side of town doesn’t want to act like he’s down.”
No, Troy’s definitely not alone (28 y.o. straight male, owns 2 Avril CDs).
-DF
Well, judging from the hiphop fans in my life, I don’t think there’s much risk that anyone will think you’re down because you listen to 50 Cent.