Composer's Note: This set of six preludes for four-hand piano was commissioned and premiered by my old friends, the husband-and-wife piano duo of Steven Pane and Yuri Funahashi. As the title suggests, each of the preludes is based on some aspect of doubling, especially that of pitch. In the final prelude, “Mezzotint,” for example, every note in the treble pianist’s right hand is simultaneously doubled in their left hand an octave and a minor third lower. The same is true for the bass pianist, except that the interval between doubled notes is an octave and a major third. Most striking are the “stretched-octave” doublings between the outer hands of the two players in “Calder,” “Toccatina,” and “Walzmärsche,” where notes in the extreme bass are paired with their treble counterparts a half step away—low G with high A-flat, for example, a pairing that sounds oddly consonant.