In Charlemagne Palestine’s landmark 1974 recording Strumming Music, the composer spends 45 minutes pounding a two-note motif, holding down the sustain pedal during the entire duration of the piece. Here, he applies these same principals of repetition and overtone, in an unusual, very moving series of compositions for the doppio borgato. “The what?” Glad you asked. The doppio borgato is a double keyboarded instrument with the piano’s normal 11 octaves on top and an additional 37 of the piano’s lowest notes, played by foot through pedals.

Disc 1 of this double CD set begins with a meditation on the piano’s highest tones, the chalky, clinking keys at the far right of the keyboard, played in gradually descending octave intervals. Succeeding compositions move downward along the keys, meditating on other octaves, other tones, and gradually introducing more complex and sustained interplay of notes. By “Tritone Octave 1/1” the sustain pedal has become an integral part of the sound, with long drones hanging over and enveloping the rapid succession of notes, and the concluding black-toned, “Tritone Octave 1/2” is as dense and ominous and moody as the initial phases “Super High Tones” were airy and precise.

The second disc is comprised of five “Cataclismas”, played on the same instrument, less rigorously tied to the octave interval, more free-ranging and, as the title suggests, explosive. These later compositions are more immediately engrossing; however, rather than cherry-picking them, it may be best to start from the beginning and move forward. The first, very rigorous explorations of this instrument’s potential acclimate you to Palestine’s approach. It is like learning to see in dim light, and as you move forward, more complex shapes and meanings emerge out of the shadows. From Etudes to Cataclysms is abtract, disciplined, intellectually challenging, yet a deeply rewarding journey, matching one of modern music’s most unusual composers to a unique and fascinating instrument.