A teenager in a black dress shirt and tie steps up to the microphone on a derelict Camden street corner and plays a trombone solo. The rest of his jazz ensemble is piped over loudspeakers, as a crowd of parents and community activists cheers over plates of barbecue.

Shortly afterward, police cars roll up. Some of the crowd has spilled into the street, and the officers tell people to move back, inciting anger from many of those in attendance at the Tuesday afternoon rally.

Ahmed Muhammad, 53, whose children are participating in the event, confronts the officers.

"There's drug dealers here and there," he says. "This is how the city supports us. By sending the police."

The performers were calling attention to a nearly decade-long dispute between the acclaimed Unity Community Center, a youth arts group that performs across the country, and the city over an outstanding tax lien on a building the group wants to use to expand in the Whitman Park section of Camden.

Despite assurances of support from city leaders - the group was honored at a City Council meeting Tuesday night - the lien remains on the property, which was donated to the group in 2000, and prohibits UCC from so much as applying for a construction permit.

But with the entrance of new Mayor Dana Redd, who took office in January, UCC leaders are putting renewed pressure on City Council to get the lien lifted.

"The whole point of this rally is to dramatize this situation for the public. It's not an attack on the mayor," said Roy Jones, a Unity board member. "Everyone's making these statements the children are our future. Well, we have to get beyond the rhetoric."

At the meeting Tuesday, City Council approved the reduction of the tax lien on the Haddon Avenue building from $202,000 to $125,000. That move was of little solace to UCC leaders, who want the whole lien gone, as well as access to federal community development funds they say they've been locked out from for years.

The lien on the 7,000-square-foot building on Haddon Avenue is controlled by the Tax Lien Financing Corp., a government-backed organization set up during the state's takeover of the city to help collect unpaid taxes.

Last year, city attorneys reviewed the situation with the UCC and determined the city had no legal remedy to help, said Patrick Keating, Camden's public works director.

"The collection, modification, or adjustment of any property owner's taxes are controlled completely by state law," read a statement from Redd's office. "The city will continue to do what is legally permissible to assist the UCC."

The continued back-and-forth over the lien has worn many UCC leaders down. They perform concerts at the Kimmel Center and the Mann Center in Philadelphia but can't get past what they perceive as a case of Camden bureaucracy gone wrong.

The lien stems from a $9,000 city water bill the building's previous owners failed to pay, Jones said.

"The rest is interest and penalties," he said.

As quickly as police showed up at Tuesday's rally, they drove off in their patrol cars. A calm returned to the crowd, who turned their attention back to the rotating cast of musicians and dancers.

Earlier in the day, Robert Dickerson, UCC's founder, commented, "We're a group dealing with hard-core inner city youth, and who cares about that?"

Contact staff writer James Osborne at 856-779-3876 or josborne@phillynews.com.