In his original program notes for Sonatra, composer Michael Gordon writes that he conceived of the piece for solo piano as a sideways tribute to Frank Sinatra, but with the sonata form as an equal and opposite force that tugs at the music from within. 'I grew up playing, or mis-playing, the piano,' he notes. 'When I started writing Sonatra, I decided that since I would probably only ever write one piano piece in my entire life, I wanted to use all the keys on the piano, and use them often. I constructed long chains or links of major and minor thirds that ceaselessly wind their way up and down the piano. Eventually they start cascading and intersperse with glissandos half the length of the keyboard, sounding to me like the performer has at least four hands.' Sonatra is slightly more than 15 minutes in length, but when performed in both equal temperament and just intonation, as Bang on a Can All-Stars pianist Vicky Chow has done for her singular recording of the piece, it takes on the aura and personality of a two-part epic. 'It's by far the most challenging piece of music I've worked on,' she says. 'When I first looked at the score, I knew immediately that I'll live with it for the rest of my life. Every few months, I slowly worked up each section, like chipping away at a slab of marble. I had to pace myself, push myself, and be sharp at every twist and turn, or else I'd trip and fall flat on my face. Performing it with just intonation adds another hurdle to overcome, because you can easily feel as though the arpeggios spiraling up and down the length of the keyboard are wrong. It adds one more sadistic layer to the traumatic physical experience a pianist or any other musician or athlete puts themselves through when trying to achieve an impossible feat. This is one of those pieces.'