The Labour leader - who campaigned for a second referendum following the Brexit vote - picked Beethoven’s ‘Ode To Joy’ during an interview with Classic FM.
He said it has “got a sense of destiny and is hugely optimistic”.
But the Conservatives mocked the choice by claiming it was evidence of Starmer’s continued affection for the EU.
Tory chairman Richard Holden said it was “simultaneously totally naff and completely telling”.
Matt Vickers, the Tory MP for Stockton South, said: “It should come as no surprise that Sir Keir is dancing to Brussels’ tune.
“Sir Keir spent years trying to block Brexit and overturn the largest democratic vote in this country’s history. Clearly, he still can’t get over his obsession.
“Labour will do everything they can to lead us back into the EU - only the Conservatives can be trusted to protect the will of the people.”
But a Labour source told HuffPost UK: “Ode To Joy is a masterpiece and one of the most important pieces of music in the western canon.
“Considering Keir is a classically trained musician, I doubt he chose it because of the EU.”
Listen to the full Starmer interview on ‘Moira Stuart Meets’ on Sunday at 9pm on Classic FM