kinship to a major work by Johann Sebastian Bach: "Digging into the lower registers of the instrument, it takes flight in handfuls of notes, now gentle, now impassioned, variously evoking the minor-mode keening of klezmer music and the interior meditations of Bach's cello suites". Glass himself pointed out "in many ways it owes more to Schubert than to Bach". In 2007, Glass also worked alongside Leonard Cohen on an adaptation of Cohen's poetry collection Book of Longing. The work, which premiered in June 2007 in Toronto, is a piece for seven instruments and a vocal quartet, and contains recorded spoken word performances by Cohen and imagery from his collection. Appomattox, an opera surrounding the events at the end of the American Civil War, was commissioned by the San Francisco Opera and premiered on October 5, 2007. As in Waiting for the Barbarians, Glass collaborated with the writer Christopher Hampton, and as with the preceding opera and Symphony No. 8, the piece was conducted by Glass's long-time collaborator Dennis Russell Davies, who noted "in his recent operas the bass line has taken on an increasing prominence,... (an) increasing use of melodic elements in the deep register, in the contrabass, the contrabassoon—he's increasingly using these sounds and these textures can be derived from using these instruments in different combinations. ... He's definitely developed more skill as an orchestrator, in his ability to conceive melodies and harmonic structures for specific instrumental groups. ... what he gives them to play is very organic and idiomatic." Apart from this large-scale opera, Glass added a work to his catalogue of theater music in 2007, and continuing—after a gap of twenty years—to write music for the dramatic work of Samuel Beckett. He provided a "hypnotic" original score for a compilation of Beckett's short plays Act Without Words I, Act Without Words II, Rough for Theatre I and Eh Joe, directed by JoAnne Akalaitis and premiered in December 2007. Glass's work for this production was described by The New York Times as "icy, repetitive music that comes closest to piercing the heart". 2008–present: Chamber music, concertos, and symphonies 2008 to 2010 Glass continued to work on a series of chamber music pieces which started with Songs and Poems: the Four Movements for Two Pianos (2008, premiered by Dennis Davies and Maki Namekawa in July 2008), a Sonata for Violin and Piano composed in "the Brahms tradition" (completed in