In just about EVERY musical there's a scene where women dance and sing in their chones. You don't believe me? I'LL PROVE IT! It starts way back when, when no woman would hang out with other women, unless they were all gonna be nearly-nude. Here are some examples.
In the song, "Many a New Day," Laurie and a swarm of scantily clad ladies dance and sing about how Laurie isn't going to kill herself over a dude. Why are they in their undies? Because they're changing to go to a dance. Duh!
Seven Brides for Seven Brothers (right)
The song is, "When You Marry in June," and frolicking around and singing is about... six women in their underwear. They're singing about how wonderful it is to get married in June, (as if they would know,) and they're almost naked because..........................
Guys N Dolls
Adelaide, as you know, works as a night club singer/dancer with a host of sub-singers/dancers. One of their numbers is, "Take Back Your Mink," and as they sing about how shocked they were that their boyfriends wanted "payment" for gifts, they strip to their panties. That makes sense.
For some reason, "The Cell Block Tango" must be performed in lingerie. Why would women in a prison not sing about the men they killed in their "evening" wear?
A bunch of women sing about getting married before they're 25. Well... why wouldn't they? The song is, "Waitin' for Me Dearie."
Les Misérables (below)
In "Lovely Ladies" a gang of prostitutes sing about themselves, and persuade Fantine to join them. And,
yes, they're almost nude.
My Fair Lady
This one hardly counts, but you're gonna have to get over it. The song is, "I Could Have Danced All Night," and during the song Eliza changes into her jam-jams. It's close, and we're counting it.
The Phantom of the Opera
During "Angle of Music," and "The Phantom of the Opera," Christine wanders around in her robe.
The Sound of Music
"Maria" is sung by a bunch of nuns and... oh wait, no. They're totally covered. Never mind.