Singer Paul Rodgers said the group wants the concert to become a tribute to the “extraordinary response” of the police officers, firefighters and paramedics who helped the victims of last Thursday’s subway and bus bombings.

“We feel it is fitting to thank London’s emergency services for their extraordinary response in dealing with the effects of the bombing attacks and to celebrate the historical resilience of Londoners in their response to yet another atrocity,” Rodgers said in a statement.

Guitarist Brian May said the band was “unbelievably shocked and saddened” to return on Thursday morning from a concert in Germany and see London under siege.

“The heroes that day, and since then, are the police and emergency services coming together as one, calmly and bravely dealing with the tragedy and getting London’s wheels turning again,” he said. “We’d like to offer an appreciation.”

About 85,000 people are expected to attend Friday evening’s concert, the first time the band has played in Hyde Park in 29 years.

Comedian Peter Kay, the rock band Razorlight and Justin and Dan Hawkins of the band The Darkness also will perform, organizers said.