Maria Lubicheva, head of the group Barto, told RFE/RL that she was asked by police on September 3 to come to the police station on September 6 and explain the meaning of a song she performed at the rally.
The song includes lyrics asking people if they are ready "to burn cop cars at night" as a way to deal "with those to whom laws are trash."
"We were called and asked to come to [Interior Ministry Office] to explain the meaning behind the text of our song 'Ready,'" she said. "I got in touch with a lawyer and we will go to [the office] and figure out what they want from us."
Lubicheva told RFE/RL that the police told her over the telephone that the chorus of her song was regarded as "bad."
"They said [the lyrics] could be connected to extremism, which would mean we could be punished," she said. "What will happen will only be clear after an expert's review."
According to the Russian Constitution, the punishment for "extremism" ranges from a fine to a three-year jail term.
The meeting-cum-concert in defense of the Khimki forest was attended by some 3,000-5,000 people. The protesters -- including Yuri Shevchuk, the lead singer of the group DDT -- were not allowed to use amplifiers or microphones.
During the concert, Lubicheva performed her song "I'm ready! Are you ready?" without a microphone, accompanied by a guitar without amplification.
The Russian opposition newspaper "Novaya gazeta" published part of the song that police allegedly consider "inflammatory."
To burn cop cars at night?
It's like the rules of life, a mark of good taste
In dealing with those to whom laws are trash."
Lubicheva wrote on her blog that the song is about a tragic romance "in the vein of [French singer-songwriter Serge] Gainsbourg's 'Bonnie and Clyde.'"
"The heroes of that poem are pro-opposition youth, which also represents a big part of the [Russian] people," Lubicheva added. "There is no clarion call in this reference.... Since when is a dialogue in a piece of art a call to some sort of action?"
After the protest meeting on August 22, Russian President Dmitry Medvedev ordered a halt to construction of the planned Moscow-St. Petersburg highway through Khimki forest, which is just outside of Moscow.
Lubicheva's band, Barto, is named after Agniya Barto, a well-known Soviet poet and children's book author.