Background: Daniel Barenboim (born 15 November 1942) is an Argentine-Israeli pianist and conductor who is a citizen of Argentina, Israel, Palestine, and Spain. He is the general music director of the Berlin State Opera, and the Staatskapelle Berlin; he previously served as Music Director of the Chicago Symphony Orchestra, the Orchestre de Paris and La Scala in Milan. Barenboim is known for his work with the West-Eastern Divan Orchestra, a Seville-based orchestra of young Arab and Israeli musicians, and as a resolute critic of the Israeli occupation of Palestinian territories. Barenboim has received many awards and prizes, including an honorary Knight Commander of the Order of the British Empire, France's Legion d'honneur both as a Commander and Grand Officier, and the German Grosses Bundesverdienstkreuz and Willy Brandt Award.
Context: Daniel Barenboim was born in 1942 in Buenos Aires, Argentina, to Argentinian-Jewish parents Aida (nee Schuster) and Enrique Barenboim. He started piano lessons at the age of five with his mother, continuing to study with his father, who remained his only teacher. On 19 August 1950, at the age of seven, he gave his first formal concert in his hometown, Buenos Aires.  In 1952, Barenboim's family moved to Israel. Two years later, in the summer of 1954, his parents took him to Salzburg to take part in Igor Markevitch's conducting classes. During that summer he also met and played for Wilhelm Furtwangler, who has remained a central musical influence and ideal for Barenboim. Furtwangler called the young Barenboim a "phenomenon" and invited him to perform the Beethoven First Piano Concerto with the Berlin Philharmonic, but Barenboim's father considered it too soon after the Second World War for a child of Jewish parents to be performing in Berlin. In 1955 Barenboim studied harmony and composition with Nadia Boulanger in Paris.  On 15 June 1967, Barenboim and British cellist Jacqueline du Pre were married in Jerusalem at a Western Wall ceremony, Du Pre having converted to Judaism. Acting as one of the witnesses was the conductor Zubin Mehta, a long-time friend of Barenboim. Since "I was not Jewish I had to temporarily be renamed Moshe Cohen, which made me a 'kosher witness'," Mehta recalled. Du Pre retired from music in 1973, after being diagnosed with multiple sclerosis (MS). The marriage lasted until du Pre's death in 1987.  In the early 1980s, Barenboim began an affair with the Russian pianist Elena Bashkirova, with whom he had two sons born in Paris before du Pre's death: David Arthur, born 1983, and Michael, born 1985. Barenboim worked to keep his relationship with Bashkirova hidden from du Pre, and believed he had succeeded. He and Bashkirova married in 1988. Both sons are part of the music world: David is a manager-writer for the German hip-hop band Level 8, and Michael Barenboim is a classical violinist.
Question: What was he best known for?
Answer: 

Problem: Background: Black Sabbath were an English rock band, formed in Birmingham in 1968, by guitarist and main songwriter Tony Iommi, bassist and main lyricist Geezer Butler, singer Ozzy Osbourne, and drummer Bill Ward. Black Sabbath are often cited as pioneers of heavy metal music. The band helped define the genre with releases such as Black Sabbath (1970), Paranoid (1970) and Master of Reality (1971). The band had multiple line-up changes, with Iommi being the only constant member throughout its history.
Context: While Ozzy Osbourne was working on new solo album material in 2006, Rhino Records released Black Sabbath: The Dio Years, a compilation of songs culled from the four Black Sabbath releases featuring Ronnie James Dio. For the release, Iommi, Butler, Dio and Appice reunited to write and record three new songs as Black Sabbath. The Dio Years was released on 3 April 2007, reaching number 54 on the Billboard 200, while the single "The Devil Cried" reached number 37 on the Mainstream Rock Tracks chart. Pleased with the results, Iommi and Dio decided to reunite the 1981 Mob Rules era line-up for a world tour. While the line-up of Osbourne, Butler, Iommi and Ward were still officially called Black Sabbath, the new line-up opted to call themselves Heaven & Hell, after the album of the same name, to avoid confusion. When asked about the name of the group, Iommi stated "it really is Black Sabbath, whatever we do... so everyone knows what they're getting [and] so people won't expect to hear 'Iron Man' and all those songs. We've done them for so many years, it's nice to do just all the stuff we did with Ronnie again." Ward was initially set to participate, but dropped out before the tour began due to musical differences with "a couple of the band members". He was replaced by former drummer Vinny Appice, effectively reuniting the line-up that had featured on the Mob Rules (1981) and Dehumanizer (1992) albums.  Heaven & Hell toured the U.S. with openers Megadeth and Machine Head, and recorded a live album and DVD in New York on 30 March 2007, titled Live from Radio City Music Hall. In November 2007, Dio confirmed that the band had plans to record a new studio album, which was recorded in the following year. In April 2008 the band announced the upcoming release of a new box set and their participation in the Metal Masters Tour, alongside Judas Priest, Motorhead and Testament. The box set, The Rules of Hell, featuring remastered versions of all the Dio fronted Black Sabbath albums, was supported by the Metal Masters Tour. In 2009, the band announced the name of their debut studio album, The Devil You Know, released on 28 April.  On 26 May 2009 Osbourne filed suit in a federal court in New York against Iommi alleging that he illegally claimed the band name. Iommi noted that he has been the only constant band member for its full 41-year career, and that his bandmates relinquished their rights to the name in the 1980s, therefore claiming more rights to the name of the band. Although, in the suit, Osbourne was seeking 50% ownership of the trademark, he said that he hoped the proceedings would lead to equal ownership among the four original members.  In March 2010, Black Sabbath announced that along with Metallica they would be releasing a limited edition single together to celebrate Record Store Day. It was released on 17 April 2010.  Ronnie James Dio died on 16 May 2010 from stomach cancer. In June 2010, the legal battle between Ozzy Osbourne and Tony Iommi over the trademarking of the Black Sabbath name ended, but the terms of the settlement have not been disclosed.
Question: where did they tour?
Answer:
Heaven & Hell toured the U.S. with openers Megadeth and Machine Head,