A solemn memorial, a symphony of blazing brass and an unpredictable piano concerto come together under the baton of Juanjo Mena, who makes a return to Orchestra Hall for a special treat: Bruckner’s sonorous Sixth Symphony. First, Philip Herbert’s Elegy pays tribute to the late Stephen Lawrence, who at 18 years old was killed in an act of racial violence. Then, world-renowned pianist Garrick Ohlsson plays Beethoven’s First Piano Concerto, an animated showpiece for piano filled with musical humor.