To walk downstairs into this old West Village bar is to step out of time a bit. As an amicable regular might tell you, the room first opened in the 1850s as a prostitutes’ den, became a boy bar by the 1890s, and lasted through Prohibition, when it was known as Marie’s (the “Crisis” came from the Crisis pamphlets by Thomas Paine, who died in the same house). For the past four decades, it’s plowed through as a piano joint in which neighboring gay men and musical-theater performers gather round the keys nightly and sing solo — numbers like “Stranger in Paradise” or “You’re the Top” — to create a mood of both giddiness and longing. The fanciest thing at the bar itself — which serves simple beer and simple mixed drinks — is the stunning WPA mural depicting French and American Revolution scenes, its origins unknown. Lore and mystery abound at Marie’s, and conversation easily turns to the subject of the house ghosts, or the rusty kitchen from the bar’s tavern days, or simply the dark, dank wood-beamed floor underneath, which has clearly soaked up its share of memories, and then some.