For years he has campaigned for greater understanding between Arabs and Israelis. And not so long ago the musical director of the Berlin Staatskapelle, who has performed with all the world's great orchestras but is still perhaps best known in Britain for his marriage to the cellist Jacqueline du Pre, declared that he did not believe in hope any more.
Yet under his baton tonight will not be one of the many European ensembles with which he has been associated in his long and distinguished career, but the West-Eastern Divan, the orchestra Barenboim founded in 1999 as a result of his friendship with the Palestinianintellectual Edward Said, who died four years later.
"It is a historic occasion," he says, bubbling with enthusiasm. "Our orchestra is made up of Jordanians, Israelis, Syrians, Lebanese, Egyptians. It is nothing short of a miracle. It defies the laws of possibility." Barenboim wanted the Divan, which is named after a cycle of poems by Goethe, to perform in Ramallah last year. "We nearly did it," he says. "But we couldn't because of the security situation. So to perform here, at the centre of the conflict, is a very important first step."
The timing of the concert at Ramallah's Culture Palace, which comes after triumphant performances by the Divan at the Edinburgh Festival and at the Proms, is coincidental. But Barenboim is well aware of the backdrop to tonight's concert. "I think that what happened in Gaza has to be a first step," he says. "There has to be a continuation of the process in the West Bank.
"Israel will not be free and secure until the Palestinians are free and secure. We have a choice here, because there are two peoples who have a geographic attachment to this land. Either we all kill each other, every one of us. Or we share this space."
Barenboim will not offer a view on Israel's Prime Minister, Ariel Sharon. "I try to stick to the facts, not speculate," he says. But he is unafraid to act in a manner that many Israelis find controversial. Last year he attacked the Israeli government for failing to engage in a proper dialogue with the Palestinians in a speech made in the Knesset, the Israeli parliament, when he was there to accept the Wolf Prize in Arts. His performances of Wagner, a composer seen by many in Israel as irrevocably tainted by anti-Semitism, have also provoked protests, but the West-Eastern Divan Orchestra, after a unanimous vote on it, has now played the overture to Tristan and Isolde as an encore.
For most of his life, 62-year-old Barenboim has been known for his achievements in the world of music rather than his comments off-stage. Born in Buenos Aires, he was the only child of pianists Enrique and Aida Barenboim. He first performed in public at the age of seven, and his career swiftly took off after his family moved to Tel Aviv in 1952.
He met du Pre, considered one of the foremost cellists of the 20th century, in 1966, and they were married the following year. Du Pre died of multiple sclerosis at the age of 42 in 1987. He describes a controversial film about her, Hilary and Jackie, which he has never seen, as "abhorrent".
Although Barenboim encountered very few Palestinians growing up, he was already concerned enough with their plight to disagree with Golda Meir, the then Israeli Prime Minister, when she announced in 1970 that there was no such thing as a Palestinian people. "I thought then," he has said, "you can't say these people don't exist." A chance meeting with Said in a London hotel in 1991 led to what Barenboim called an "inseparable" friendship, and later, the creation of the Divan.
"This is not a project for peace," says Barenboim, "it is a fight against ignorance. Music is not only a way to forget the world, sitting down with a double whisky and listening. It is about integration. Every musician who plays two notes, who includes dynamics, tone and pitch, is engaged in an act of integration."
In this way, Barenboim sees the Divan as having a practical purpose. "We cannot talk about ideology first," he says, "because what is required is not a political solution but a change in the mode of thinking. So don't ask which comes first, the chicken or the egg. We must make the plate warm enough so we can have both the chicken and the egg."