There is a real live Yale bohemian in Brooklyn, N.Y., with tweed earflaps dangling and a copy of the Upanishad at his feet.

Sam Grossman — Class of 2004 for sure, he said, because he promised his parents he’d come back to graduate — is living rent-free in a porkpie hat on $2 breakfast specials and Chinese fried chicken. The would-be senior is taking the year off to play guitar in the 36th Street subway station and study bartending for Manhattanites.

Grossman is an afternoon philosopher in denim Converse All-Stars and, though it’s only been a month since he started busking part-time, he’s already singing over subway trains, even when they are not there.

In a quiet coffee shop in the trendy Williamsburg section of Brooklyn, he belts an Oasis song to a pierced and pleased bartender. In Washington Square Park at midnight, he pounds out original acoustic hip-hop songs about 19th-century French painters to confused, bemused drug dealers.

Got “nothing to lose,” one song goes, “Like Lautrec.”

Last year, Grossman was a well-reviewed regular at Koffee? 2 and Cosi. An English major, he said he decided to take time away from Yale to quit smoking — “God bless the a–holes who charge $8 for cigarettes here” — and spend more time on his music. He was skipping classes as it was, he said, and “not taking full advantage of the fine resources this university has to offer.”

The first time he played the guitar on the street in New York, it was right by the Yale Club on Vanderbilt Avenue, at the door to Grand Central Terminal. He’d gone into the city to record a few songs and go to a concert that let out at 3 in the morning. He needed a bagel.

It became the idea for an unconventional semester or two abroad aboard crosstown buses and downtown trains, singing in stations for a steady $10 an hour. That first day he played a few Beatles songs that got him enough coffee to make it to a 9 o’clock class, six hours later. Now, he rises early in a room in his grandmother’s basement that has a small bathroom filled with power tools.

“When I don’t have anything to avoid in the morning,” he said, “I have no trouble waking up.”

He began with the intention of paying for his food and electricity with the money he made in the subway, but after two weeks collected only $40, enough to pay for the throat lozenges made necessary by all the singing and grime.

Now, he’s “back on the dole,” (his parents) and calling friends on a cell phone to come play bucket backup at his underground rush-hour shows. Grossman said he has networked a little in the traditional sense, as any good Yalie is wont to do, and has met some good musicians for possible collaboration.

He has also met his share of shady characters, menacing bands of kids and friendly subway psychopaths. But no more, he said, than he knew back at school.

“There are a lot of crazies in New Haven too,” he said, “and a good number go to Yale.”