Composers new to his discography included Richard Strauss, Szymanowski and Anton Bruckner—his recording of the Eighth Symphony met with particular acclaim. The most significant addition to his recorded repertoire was the multi-orchestra cycle of the Mahler symphonies and vocal works with orchestra. All of Boulez's recordings for Deutsche Grammophon have been collected into boxed sets of CDs. In 2015 DG issued a 44-CD set "Boulez—20th Century" for his 90th birthday. DVDs of two opera productions are also available on DG: the Welsh National Opera "Pelléas et Mélisande" and the Vienna "From the House of the Dead". In addition, many hundreds of concerts conducted by Boulez are held in the archives of radio stations and orchestras. Occasional releases provide a glimpse of the wealth of material they contain. In 2005, for example, the Chicago Symphony Orchestra released a 2-CD set of broadcasts by Boulez, focusing in particular on works which he had not otherwise recorded, including Janáček's "Glagolitic Mass", the suite from Debussy's "Le martyre de Saint Sébastien" and Messiaen's "L'ascension". From time to time in the early part of his career Boulez performed publicly as a pianist, usually as part of a mixed programme in which he also conducted orchestral or instrumental music. In 1955 he accompanied the tenor Jean Giraudeau in a recording of songs by Stravinsky and Mussorgsky. Between 1957 and 1959 he gave several performances of his own Third Piano Sonata (a performance he gave in Darmstadt on 30 August 1959 was issued on CD in 2016). On a number of occasions he played music for two pianos with Yvonne Loriod and in the 1960s and 1970s he occasionally included songs for voice and piano in orchestral programmes, for example accompanying Dorothy Dorow in Debussy's "Trois poèmes de Stéphane Mallarmé" at a BBC Symphony Orchestra concert in March 1966 and Christa Ludwig in songs by Berg at a New York Philharmonic Orchestra concert in February 1972. A rare example of his pianism in later life was a short film made by Austrian television in 1992, in which Boulez played his early "Notations". According to Jean-Jacques Nattiez Boulez was one of two twentieth-century composers who wrote most prolifically about music, the other being Schoenberg.