Subway musician Lester Schultz, a self-described “nut for the harmonica,” has been playing beneath the official Music Under New York banner for six years, first with his band, the El Street Café, and then solo after the band “broke up like a bad marriage.”

His MUNY pass and banner guarantee Mr. Schultz a high-traffic spot during the block of time he signs up for. If an unlicensed musician, known as a “freelancer,” is in his spot during his time block, Mr. Schultz as a MUNY member can demand that the freelancer move.

While performing in subway stations and on train platforms is legal even without an MTA-issued pass, freelancers are often forced to surrender lucrative, high-traffic spots to musicians licensed by the MUNY program, part of the MTA Arts For Transit initiative.

Competition for the good spots can get heated.

“We used to have a problem with acrobats and dancers,” Mr. Schultz said. “There’d be 10 of them, one of us, and they could do somersaults, and they didn’t care if we had a pass. They just wouldn’t leave.”

Spats between musicians also arise when freelancers do not speak English and fail to understand why they are being forced to move along, according to other MUNY musicians.

Among subway musicians, there exists a social hierarchy underground that is invisible to daily commuters and tourists. It could be compared with a high school cafeteria, where the cool clique can scare away outsiders from a designated table with a practiced eye roll (in this case, the flash of a MUNY pass).

Subway musician Natalia Paruz, who plays the musical saw, performed as a freelancer for years until she became fed up with countless tickets from the transit police and too much time and money lost while searching for a free spot. “Sometimes I’d get to my spot and someone would already be there. I’d lose an hour just trying to find another place to play,” Ms. Paruz said. Eight years ago, she joined MUNY.

Now, Ms. Paruz performs on the high-traffic mezzanine at the Times Square station. Her lips parted slightly, it is difficult to tell whether it is she or her saw producing the eerie sound (it is, in fact, the saw that is singing).

As a former freelancer herself, Ms. Paruz tries to avoid altercations with freelancers if they accidentally occupy her spot during her time block. “If someone is here when I get here, I tell them, ‘I’m sorry.’ Often, they’re understanding and they’ll move on,” she said.

“With the banner, you know there’s a spot waiting for you, which is really nice,” she said. MUNY musicians are allowed to sell their CDs underground, a privilege not extended to freelancers, according to the MUNY and Arts for Transit manager, Lydia Bradshaw.

In the underground corridor along 14th Street between Sixth and Seventh avenues, accordion player Galen Peria performs as the people come and go. “I’m not a MUNY member. I just started this today as a way to make money to go to India to visit my pregnant girlfriend,” Mr. Peria said. Because he considers this a short-term gig, he plans to continue as a full-time freelancer over the next couple weeks and make as much money as possible. While no one knows exactly how much money subway musicians take in, the more successful acts report banking about $70 for three hours.

Mr. Peria was lucky to choose a spot that is not one of the 25 locations where MUNY members get priority. “I just chose this spot because I liked the acoustics in this tunnel,” Mr. Peria said.

In the end, both MUNY musicians and freelancers “help a lot of folks take the edge off of their day,” the senior attorney for the Straphangers Campaign, Gene Russianoff, said. “And it all feels very New York.”