Striking a compromise between local musicians and residents, the City Council Monday amended and then approved a detailed ordinance to regulate street performances in Harvard Square.

The law, passed by a vote of six to two, marks the first time Cambridge has sanctioned the use of electronic amplifiers by street musicians. It also establishes performance sound levels, an 11 o'clock curfew and a $25 fine for each infraction of the law.

The ordinance supercedes an old one, which prohibited the use of amplifiers but had ceased to be enforced upon a legal challenge that it was unconstitutional.

At Monday's meeting, the Council passed several amendments introduced by Councilor Francis H. Duehay '55, the ordinance committee chair who has been the driving force, behind the bill for the past few months. Duehay's amendments were apparently aimed at quelling the fears of angry musicians, who felt the new law might effectively prohibit their performances altogether.

Accordingly, the new law stipulates that nightime noise measurements be monitered from inside a residential dwelling. Originally, the Council proposed to enforce its 50 decibel noise ceiling by measurements taken from outside, a move Stephen Baird, president of the Street Artists Guild, had said "reduced the First Amendment to a whisper."

In addition, the council took back its original recommendation to punish two-time violators by suspending their licences for 30 days. Without much debate, the Council instead decided to impose a $25 fine for each infraction.

"I would have liked to see something forfrequent violators," said Councilor Jonathan S.Myers. But he added, "Two times could have been anaccident."

Several performers contacted this week saidthey felt the new law was reasonable, althoughsome called the 11 o'clock cufew excessivelystringent. The Council voted down an attempt byMyers to allow performances until midnight.

However, another section of the new ordinanceprohibiting performances altogether in one stretchof the Square has evoked vehement criticism. Underthe new law, performances are forbidden alongBrattle St., from Church St. to just past theAmerican Repertory Theatre.

Dianna Stallone, the guild's legal counsel,told the Council that the prohibition was toobroad to withstand a challenge in the courts.

"We have never taken the position that allrights are absolute," she said. But she warnedthat the law gave residents an "absolute right toprevent street music outside their home."

"Absolute bans on First Amendment rights areunconstitutional," she said at the meeting. "Ifyou adopt this ban, it can and will be attacked."

But Councilor William H. Walsh, himself alawyer, disputed Stallone's estimate of the law'sconstitutionality, saying "she thinks everythingis unconstitutional."

"There are reasonable restrictions available tothe public for loud music," Walsh said in aninterview. "I feel that's very much the casehere."

Stallone said the guild is planning to vote onwhether it will bring a suit against the city. Ifit decides not to sue, she said, it might ask fora city-wide referendum on whether the performersmay play in the excluded area, or it mightotherwise decide to boycott the city altogether.