An old man plays his cello at the foot of a crumbling wall. The notes of the sarabande of Bach’s Suite No 2 rise in the cold air, praising God for the “miracle” of the fall of the Berlin Wall, as Mstislav Rostropovich later put it. The photograph is seen around the world. The date is 11 November 1989, and the Russian virtuoso is marching to the beat of history.

Publicity stunt or political act? No doubt a bit of both – and proof, in any case, that music can have a political dimension. Yo-Yo Ma showed as much in September when the cellist opened the new season of the Philharmonie de Paris with the Boston Symphony Orchestra. As a “messenger of peace” for the United Nations, the Chinese American is the founder of Silk Road Project, which trains young musicians from a variety of cultures to listen to and improvise with each other and develop a common repertoire. “In this way, musicians create a dialogue and arrive at common policies,” says analyst Frédéric Ramel, a professor at the Institut d’Études Politiques in Paris. By having music take the place of speeches and peace talks, the hope is that it will succeed where diplomacy has failed.

At the Philharmonie, the Boston Symphony Orchestra performed Shostakovich’s Symphony No 10. The Soviet composer’s output mirrored the history of 20th-century international relations. In 1941, with Stalingrad under siege, he wrote his seventh symphony, which quickly became a symbol of Soviet resistance to the Nazi invasion. The score made it to the west on microfilm via Tehran and was played in London and New York before being broadcast on loudspeakers in Stalingrad in August 1942. The objective: to offer moral support to the population and to discourage the enemy occupiers. Mission accomplished. When the Germans tried to disrupt the broadcast, the Soviets responded with cannon fire, to the joy of the city’s inhabitants.

Musicians create a dialogue and arrive at common policies Frédéric Ramel, political analyst

Curiously, the study of the role of music in international relations is still in its infancy. “Historians must have long seen it as something fanciful, because history has long been dominated by interpretations that stress economic, social and political factors,” says Anaïs Fléchet, a lecturer in contemporary history at the Université de Versailles-St-Quentin and co-editor of a book about music and globalisation.

“As for musicologists,” she adds, “until quite recently they were more interested in analysing musical scores than the actual context in which these were produced and how they were received.” In the 1990s came a cultural shift. Scholars were no longer interested solely in “hard power” – that is, in the balance of powers and in geopolitics – but also in “soft power”, where political issues are resolved by mutual support rather than force.

Only at the start of this decade did music find its way into the study of international relations. A little late, perhaps? “When it comes to analysing non-textual musical sources, historians have tended to shy away,” Fléchet says. “In a way they’re afraid they don’t possess enough technical tools to grasp what music is.” Yet, in many ways, musical soft power has existed since at least the 17th century, starting with the birth of opera. One of the functions of this Italian art form was to project the power of the princes of the time. Back then diplomats required some musical training. “There were treatises,” says Ramel, “that indicated that they had to learn to ‘play like a viola’ – in other words, to show restraint and elegance.”

A big change came after the first world war, when Woodrow Wilson proclaimed an end to “secret diplomacy” between nations and the start of “open diplomacy”. In democratic states, music now needed to touch people directly. In the 1960s, for example, during the cold war, the US State Department organised international tours of American jazz musicians. “Perhaps,” Ramel speculates, “it was a way to project an image of the free world founded on pluralistic values and identities.”

Gilberto Gil sings while then UN secretary general Kofi Annan plays percussion at a September 2003 concert at the UN headquarters honouring those killed by a bomb at a UN office in Baghdad a month earlier. Photograph: Zuma/Alamy

Since then, every embassy has a cultural attache. The US engages in “audio diplomacy” by financing hip-hop festivals in the Middle East. China promotes opera in neighbouring states to project an image of harmony. Brazil has invested in culture to assert itself as a leader in Latin America, notably by establishing close collaboration between its ministries of foreign affairs and culture; musician Gilberto Gil was culture minister during Luiz Inácio Lula da Silva’s presidency from 2003 to 2008. He was involved in France’s Year of Brazil. As Fléchet recalls, “the free concert he gave on 13 July, 2005 at the Place de la Bastille was the pinnacle. That day, he sang La Marseillaise in the presence of presidents Lula and Jacques Chirac.” Two years earlier, in September 2003, Gil sang at the UN in honour of the victims of the 19 August bombing of the UN headquarters in Baghdad. He was delivering a message of peace, criticising the war on Iraq by the US: “There is no point in preaching security without giving a thought to respecting others,” he told his audience. Closing the concert, he invited then UN secretary general Kofi Annan on stage for a surprise appearance as a percussionist. “This highly symbolic image, which highlighted the conviction that culture can play a role in bringing people together, shows how music can become a political language,” Fléchet says.

Like Gil, Senegalese musician Youssou N’Dour was named culture minister of his country, in 2012. A cabinet member, he has a mission to promote Senegal’s image abroad. “When I started out in music, politics didn’t interest me,” he says. That changed when, in 1988, he was invited to participate – along with Bruce Springsteen, Sting, Peter Gabriel and Tracy Chapman – in Amnesty International’s Human Rights Now! tour of 14 countries.

It’s impossible for me to think of art as simply entertainment; it bears witness to our times. Angélique Ionatos, singer-songwriter

More than a million people came to the concerts, and close to a billion watched on TV. “On the border of Chile, which was then under the yoke of General Pinochet, the wives of men killed or imprisoned by the regime who had managed to cross the border came up on stage,” N’Dour recalls. “I saw just how much music could carry a message. Ever since then, in my songs, I’ve spoken about Senegalese society. Today I see my concerts as a kind of hyphen between Africa and the west, whose consciousness I want to raise about the resources and the vitality of our continent – just as I do, at another level, in my meetings with heads of state.”

Some artists take political stands without representing any country in particular. “It’s impossible for me to think of art as simply entertainment; it bears witness to our times,” says Angélique Ionatos, a Greek singer-songwriter who lives in Paris. In her new album Reste la lumière she sings the words of her country’s poets, in Greek. “Take courage, my doves, my anemones, my beautiful forsaken companions, my Antigones!” These lines from Nobel Prize-winning poet Odysseas Elytis resonate with contemporary Greek reality. “It’s as if they were written today,” says Ionatos. “After my concerts, people come up to talk to me with tears in their eyes.”

On 9 September, it was Franco-Syrian flute player Naïssam Jalal’s turn to perform at the Philharmonie de Paris, and her playing evoked another political reality. With her multicultural quintet Rhythms of Resistance, a group bridging east and west, Jalal performed a suite she wrote in 2011 inspired by the Syrian revolution. “The images that form the basis of my music come flooding back in the minds of my listeners,” she says. “In Syria, the people close to me who fought for democracy and who hoped to live in a free country actually thank me. They have the impression that I speak for them.”

Jewish and Arab musicians of the West-Eastern Divan Orchestra, perform during a solidarity concert in the West Bank city of Ramallah, in 2005. Photograph: Abbas Momani/Getty

The goal of these artists is to shake up politics, and it helps if a musician has a specific political project. Among the major figures of contemporary musician-diplomats is the Israeli-Argentinian conductor Daniel Barenboim. In the 1990s, Barenboim met a kindred soul, the militant Palestinian ––intellectual Edward Said. Finding common ground in the belief that music can defuse conflicts that conventional diplomacy cannot, they established the West-Eastern Divan Orchestra, made up of young musicians from Israel and its Arab neighbours who were keen to learn from one another and play together. In 2005, the orchestra gave a concert in the Palestinian Territories. To get into the West Bank, the musicians had to be issued diplomatic passports. And an unusual situation occurred: some of the Israelis were put under the protection of the Palestinian police. Despite its success, Arab countries in the region stopped supporting the orchestra after Israel attacked Lebanon in 2006. And opinion in Israel is divided over Barenboim himself. Some have opposed his audacious decision to play Wagner in Israel, while others have objected to his stands against the country’s policy of expansionism. Despite everything, the orchestra continues to tour. “Undoubtedly, Barenboim has no direct political influence,” says Ramel, “but he has created a new political consciousness that is extremely powerful.”

As long as it generates media coverage, musical diplomacy can attract attention to political and social problems – and make a real impact on international policy. On tours that have coincided with meetings of the G7 or G8 countries, for instance, Bono, the frontman of Irish rock group U2, managed to get part of Africa’s financial debt erased by raising awareness among audiences and governments to the suffering of the African peoples.

Musicians are keen to get produced in the west. It’s a way for them to save their culture in the face of globalisation Alain Weber, artistic adviser at Philharmonie de Paris

Another example: at the 2015 Eurovision Song Contest, Armenia, which this year is commemorating the 100th anniversary of the 1915 genocide, submitted as its official entry a song titled Don’t Deny. It was to be performed by Genealogy, a group made up of five members of the Armenian diaspora in France, Ethiopia, the US, Japan and Australia, as well as one Armenian. At the request of Turkey and Azerbaijan, which do not recognise the genocide, Armenia was forced to change to the title of the song to Face the Shadow. “We just wanted to show, thanks to Eurovision, that we are standing tall, all over the world,” says the singer Essaï Altounian, who represented the Armenians of Europe at the show; her grandfather survived the genocide by fleeing across the Syrian desert. Music is also a way for some disappearing cultures to stay alive, particularly in a world that’s becoming increasingly globalised. “Today, in the remote regions of the world, musicians are very keen to get produced in the west, which was not the case 20 or even 10 years ago,” says Alain Weber, the Philharmonie de Paris’s artistic adviser on world music. “It’s a way for them to save their culture in the face of globalisation.”

It should come as no surprise, then, that music plays a particularly strong role during cultural and ethnic conflicts. Sivan Perwer is the most popular singer of his generation in Kurdistan and the Kurdish diaspora. “Even if his more traditional songs are now allowed to be played in Turkey, most of his repertoire continues to be banned there and in Iran,” says Weber. “Yet despite the risks, the Kurds themselves have never stopped listening to them.”

The self-declared Islamic State, whose militants burn musical instruments, understands the power of sounds and singing. During last winter’s attack on the Kurdish town of Kobani, in Syria, the French journalist Edith Bouvier witnessed a frail young Kurdish militant suddenly break into song about love and war – then burst into laughter.

“They hate it when we sing,” the girl told her. “We heard them on their walkie-talkies the other day say that the devils had arrived. They were talking about us.”

This article appeared in Guardian Weekly, which incorporates material from Le Monde

• This article was amended on 10 November 2015. An earlier version referred to Yo-Yo Ma, rather than the Boston Symphony Orchestra, performing Shostakovich’s Symphony No 10.