“I think it’s a celebration of summer,” violinist Ken Hamao says. “The Tchaikovsky’s got a kind of warm exuberance, right from the opening - it’s almost like a chorale. And everyone knows the Borodin from the beautiful melodies.”Hamao is talking about the Parker Quartet’s upcoming program - Tchaikovsky’s first quartet, and Borodin’s second - in Boylston’s Summer Star Wildlife Sanctuary.