If you have ever been to a birthday party and heard two people singing Happy Birthday together, except they each started on a different note, than you already know what bitonality is. I’ve enlisted my friend Steve to help me demonstrate this!
Bitonality is simply playing in two keys at the same time. Bernstein loved these clashes; he called bitonality “exciting” and, referring to a piece called Saudade do Brasil by French composer Darius Milhaud, he wrote, “…the left hand in G and the right hand in D… do you see how charming and relaxed bitonality can be?” (The Unanswered Question pg 361)
Listen to Bernstein himself explain bitonality at 1:06 in the video to the left of his Young People’s Concert.
You can find moments of bitonality peppered throughout the Serenade, but a great example is the duet between the violin and cello (played in this short excerpt by the piano) at the beginning of the Socrates movement. (1:20 on the recording). The violin starts on an F. The cello plays the same melody but starts on an A.