In the beginning of his career, Barenboim concentrated on music of the classical era, as well as some romantic composers. He made his first recording in 1954. Notable classical recordings include the complete cycles of Mozart, Beethoven and Schubert's piano sonatas, and Mozart's piano concertos (in the latter, taking part as both soloist and conductor). Romantic recordings include Brahms's piano concertos (with John Barbirolli), Mendelssohn's Songs Without Words, and Chopin's nocturnes. Barenboim also recorded many chamber works, especially in collaboration with his first wife, Jacqueline du Pre, the violinist Itzhak Perlman, and the violinist and violist Pinchas Zukerman. Noted performances include: the complete Mozart violin sonatas (with Perlman), Brahms's violin sonatas (live concert with Perlman, previously in the studio with Zukerman), Beethoven's and Brahms's cello sonatas (with du Pre), Beethoven's and Tchaikovsky's piano trios (with du Pre and Zukerman), and Schubert's Trout Quintet (with du Pre, Perlman, Zukerman, and Zubin Mehta).  Notable recordings as a conductor include: the complete symphonies of Beethoven, Brahms, Bruckner, Schubert and Schumann, the Da Ponte operas of Mozart, numerous operas by Wagner, including the complete Ring Cycle, and various concertos. Barenboim has written about his changing attitude to the music of Mahler; he has recorded Mahler's Fifth, Seventh and Ninth symphonies and Das Lied von der Erde. He has also performed and recorded the Concierto de Aranjuez by Rodrigo and Villa-Lobos guitar concerto with John Williams as the guitar soloist.  By the late 1990s, Barenboim had widened his concert repertoire, performing works by baroque as well as twentieth-century classical composers. Examples include: J.S. Bach's The Well-Tempered Clavier (which he has played since childhood) and Goldberg Variations, Albeniz's Iberia, and Debussy's Preludes. In addition, he turned to other musical genres, such as jazz, and the folk music of his birthplace, Argentina. He conducted the 2006 New Year's Eve concert in Buenos Aires, in which tangos were played.  Barenboim has continued to perform and record chamber music, sometimes with members of the orchestras he has led. Some examples include the Quartet for the End of Time by Messiaen with members of the Orchestre de Paris during his tenure there, Richard Strauss with members of the Chicago Symphony Orchestra, and Mozart's Clarinet Trio with members of the Berlin Staatskapelle.  To mark Barenboim's 75th birthday, Deutsche Grammophon released a box set of 39 CDs of his solo recordings, and Sony Classical issued a box set of Barenboim's orchestral recordings on 43 CDs and three DVDs in 2017, Daniel Barenboim - A Retrospective.

Answer this question "What else is significant about his style?" by extracting the answer from the text above.
By the late 1990s, Barenboim had widened his concert repertoire, performing works by baroque as well as twentieth-century classical composers.