Answer by taking a quote from the following article:

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.

Barenboim has performed several times in the West Bank: at Bir Zeit University in 1999 and several times in Ramallah.  In December 2007, Barenboim and 20 musicians from England, the United States, France and Germany, and one Palestinian were scheduled to play a baroque music concert in Gaza. Although they had received authorization from Israeli authorities, the Palestinian was stopped at the Israel-Gaza border and told that he needed individual permission to enter. The group waited seven hours at the border, and then canceled the concert in solidarity. Barenboim commented: "A baroque music concert in a Roman Catholic church in Gaza - as we all know - has nothing to do with security and would bring so much joy to people who live there in great difficulty."  In January 2008, after performing in Ramallah, Barenboim accepted honorary Palestinian citizenship, becoming the first Jewish Israeli citizen to be offered the status. Barenboim said he hoped it would serve as a public gesture of peace. Some Israelis criticized Barenboim's decision to accept Palestinian citizenship. The parliamentary faction chairman of the Shas party demanded that Barenboim be stripped of his Israeli citizenship, but the Interior Minister told the media that "the matter is not even up for discussion".  In January 2009, Barenboim cancelled two concerts of the West-Eastern Divan Orchestra in Qatar and Cairo "due to the escalating violence in Gaza and the resulting concerns for the musicians' safety."  In May 2011, Barenboim conducted the "Orchestra for Gaza" composed of volunteers from the Berlin Philharmonic, the Berlin Staatskapelle, the Orchestra of La Scala in Milan, the Vienna Philharmonic and the Orchestre de Paris--at al-Mathaf Cultural House. The concert, held in Gaza City, was co-ordinated in secret with the United Nations. The orchestra flew from Berlin to Vienna and from there to El Arish on a plane chartered by Barenboim, entering the Gaza Strip at the Egyptian Rafah Border Crossing. The musicians were escorted by a convoy of United Nations vehicles. The concert, the first performance by an international classical ensemble in the Strip, was attended by an invited audience of several hundred schoolchildren and NGO workers, who greeted Barenboim with applause. The orchestra played Mozart's Eine kleine Nachtmusik and Symphony No. 40, also familiar to an Arab audience as the basis of one of the songs of the famous Arab singer Fairuz. In his speech, Barenboim said: "Everyone has to understand that the Palestinian cause is a just cause therefore it can be only given justice if it is achieved without violence. Violence can only weaken the righteousness of the Palestinian cause".

Can you tell me anything else about the Orchestra for Gaza?
composed of volunteers from the Berlin Philharmonic, the Berlin Staatskapelle, the Orchestra of La Scala in Milan, the Vienna Philharmonic and the Orchestre de Paris--at al-Mathaf Cultural House.