7 "Toltec" (2004), and the song cycle Songs of Milarepa (1997) have a meditative theme. The operatic Symphony No. 6 Plutonian Ode (2002) for soprano and orchestra was commissioned by the Brucknerhaus, Linz, and Carnegie Hall in celebration of Glass's sixty-fifth birthday, and developed from Glass's collaboration with Allen Ginsberg (poet, piano—Ginsberg, Glass), based on his poem of the same name. Besides writing for the concert hall, Glass continued his ongoing operatic series with adaptions from literary texts: The Marriages of Zones 3, 4 and 5 ([1997] story-libretto by Doris Lessing), In the Penal Colony (2000, after the story by Franz Kafka), and the chamber opera The Sound of a Voice (2003, with David Henry Hwang), which features the Pipa, performed by Wu Man at its premiere. Glass also collaborated again with the co-author of Einstein on the Beach, Robert Wilson, on Monsters of Grace (1998), and created a biographic opera on the life of astronomer Galileo Galilei (2001). In the early 2000s, Glass started a series of five concerti with the Tirol Concerto for Piano and Orchestra (2000, premiered by Dennis Russell Davies as conductor and soloist), and the Concerto Fantasy for Two Timpanists and Orchestra (2000, for the timpanist Jonathan Haas). The Concerto for Cello and Orchestra (2001) had its premiere performance in Beijing, featuring cellist Julian Lloyd Webber; it was composed in celebration of his fiftieth birthday. These concertos were followed by the concise and rigorously neo-Baroque Concerto for Harpsichord and Orchestra (2002), demonstrating in its transparent, chamber orchestral textures Glass's classical technique, evocative in the "improvisatory chords" of its beginning a toccata of Froberger or Frescobaldi, and 18th century music. Two years later, the concerti series continued with Piano Concerto No. 2: After Lewis and Clark (2004), composed for the pianist Paul Barnes. The concerto celebrates the pioneers' trek across North America, and the second movement features a duet for piano and Native American flute. With the chamber opera The Sound of a Voice, Glass's Piano Concerto No. 2 might be regarded as bridging his traditional compositions and his more popular excursions to World Music, also found in Orion (also composed in 2004). 2005–2007: Songs and Poems Waiting for the Barbarians, an opera from J. M. Coetzee's novel (with the libretto by Christopher Hampton), had its premiere performance in September 2005. Glass defined the work as a "social/political opera", as a critique on the Bush administration's