When Loretta Dranoff, founder of the biennial Murray Dranoff International Two Piano Competition in Miami, asked me to compose a test piece for her event, I was initially at a loss. I had composed one previous work for two pianos, Kaleidoscope, in 1959, and couldn’t think of anything else I wanted to say in that medium. I couldn’t see what made a second piano so important. It was the same sound; it was simply a matter of adding another player. I couldn’t reconcile why I should write for two pianos when I could write as well for one.
Eventually, the deadline forced me to come up with a solution. What occurred to me, finally, was the idea to change totally the concept of two pianos by ‘preparing’ one of them. This was not to be a prepared piano in the John Cage sense, with objects inserted between the strings. Instead, one of the pianos would be tuned a quarter-tone lower than the other, in other words, each piano would sound perfectly tuned by itself, but, for example, the note G on one piano would sound at a pitch between G and F sharp on the other piano, creating eerie effects and dissonances when the instruments were played together.
Quarter-tones are readily (and sometimes unintentionally) produced by violinists and singers, but they rarely appear in piano music, because of the instruments fixed pitches. Charles Ives experimented with them, and they appear in Bartok’s classic string quartets. I have only made use of them twice before, in my (first) film score for Altered States, and in the opening star music of Pied Piper Fantasy, my concerto for flute and orchestra from 1982. In those contexts, I liked the eerie, hallucinatory quality the mistuning evoked. For Chiaroscuro, however, I wanted to use quarter-tone music expressively, as well as to make it a startling device. I was looking for the expressive power between two notes, like a blues singer does.
So, a brief annunciatory opening sets up a dreamy, ardent slow movement in which the sighing semitones that classical music has always used to express mourning are subdivided into quarter-tones for an effect I thought both subtler and more intense. The third movement interrupts a stabbing toccata in the competing C minor keys of the two different pianos by bringing, for a moment, both pianists together to play on one piano. Here the music quotes a choral by Bach, symbolic of our stable and traditional harmony (even though, while both pianists are playing at last in the same key, they are still subtly out of rhythmic phase, as one player’s crotchet equals the other’s dotted quaver). But before long, the surrealism of quarter-tone harmonies returns, as each pianist seems to fight to define his or her tuning as tonic. All is resolved, though, in the percussive cluster of the final gesture.
– John Corigliano