An interesting cultural twist to singing in public places crops up at my workplace. I, too, work in a Federal enclave, and we have a very racially and ethnically diverse crowd of people here at NIH. I will frequently hear black Americans un-selfconsciously belting out a song in the hallway, or singing along with a Walkman, but have NEVER heard a white American do the same. I (being white)find myself intimidated when I'm singing in a hallway or elevator and encounter another person, and immediately clam up (or at least drop the volume to a mumble).Any number of my co-workers (again, mostly WASP) look on singing as something that's done by Professionals, and you hear them say "Oh, I can't carry a tune" or "My grade-school teacher told me to just mouth the words and not make noise, so I must be terrible." (It's incredible the amount of damage some teachers can do...) When people here found out I sing, and sometimes even perform at folk festivals, they automatically started expecting me to lead "Happy Birthday" at office parties - as if no-one else could possibly start to sing a song EVERYONE knows. Lately, I've gotten stubborn and have refused to be the one who starts it, but join in in harmony once it gets going, in hopes that folks will realize it's okay for them to start a song if they want to!
I think that a lot of folks probably sing along with the radio in the privacy of their cars (I do, but maybe I'm just weird), but are afraid to sing in front of others, for whatever reason. This is a shame, for the "Professionals" the recording industry pushes aren't always very good themselves, but are out on the airways through some chance combination of timing, good promotion and sheer luck, rather than musical ability or talent.
Tolerance for singing along at live performances varies from place to place, too. I remember going to Passim's while on a business trip to Boston many years ago. Bill Staines was playing, doing his relaxed collection of songs, most with wonderful choruses. I started to sing along on the choruses, as we all do here in Washington, but quickly stopped when I found myself VERY alone in that audience. That may have been club policy; at the Birchmere here in DC, they have little signs on all the tables telling people to shut up "while the performances(sic) are on stage". But at any of the concerts put on by the Folklore Society, as Lorraine and BillD have mentioned, joining in is enthusiastically appropriate.
So, is singing aloud a regional thing, or a racial thing, or an educational thing?