They say that if you want to understand a revolution, you have to listen to its music. Over the past year, as people's movements and student uprisings have swept through Europe and now America in response to the global crisis of capitalism, I have lost count of the number of grumbling articles by middle-aged, male columnists, complaining about the movement's lack of a defined soundtrack. There is no troubadour for this new, networked uprising, no Dylan or Billy Bragg for everyone to hum along to.

This is the charge being put to the protests that have sprung up in cities across the world following Occupy Wall Street: there is no defining ideology, no list of demands, so the movement must be inarticulate, and can be easily dismissed. If we don't know the song, how can we sing along? In fact, if you walk down to your nearest occupation - and as occupations are ongoing across the country, that should not be hard - you will find it full of music.

At the Occupy London protest on Ludgate Hill, I saw people playing reggae and jazz as occupiers of all ages huddled in sleeping bags, fighting off the wind chill under a giant banner reading "Capitalism Is Crisis".

In Liberty Plaza, at the Occupy Wall Street camp in the shadow of Manhattan's financial district, I saw the young unemployed from the Bronx clapping along to an impromptu string-and-woodwind band's rendition of Woodie Guthrie's "This Land Is Our Land", which segued without pause, and to much applause, into violent modern punk. Elsewhere, a boy of 17 with flowers in his hair sat, entirely unironically, bashing out the chords to Bob Dylan's "The Times, They Are a-Changin'" on a guitar with four strings left. Around him, a gang of union members, hippies and Wall Street workers sang along.

Not that young people aren't writing riot songs, too. Grime, rap and dubstep have been the soundtrack of the British student movements just as much as rousing traditional folk tunes. There is a sense of time speeding up, of a collision of possible futures. In his book Retromania, the music critic Simon Reynolds observes that the range and quantity of music easily accessible online or in digital format at any one moment gives a sense of all of pop history happening at once. People travel to their office jobs carrying pocket playlists stuffed with Sinatra, Shostakovitch and the Streets.

Vinyl vanguard

This new protest movement - organised online and drawing in interest groups from unions to militant student groups and angry individuals holding placards criticising health-care reform - gives a similar impression of every uprising happening at once. I was in Madrid as 60,000 people crammed into Puerta del Sol, and middle-aged women brandishing copies of communist newspapers marched with masked anarchists in black and young organisers from the ¡Democracia Real Ya! arm of the summer's 15M uprising.

There are too many different tunes being sung for one melody to be audible over the noise of marching feet. To the political old guard, it can seem that the normal progression of events has become jumbled. The troops of this new uprising have not waited for a defined ideology or specific list of demands. How could they? The problems they have come together to protest against are too great - the disintegration of representative democracy, cuts to welfare, housing, health care and education propping up the oligarchy of aggressive market finance.

What marks this form of social change is precisely its pluralism, its rejection of conventional politics, its abhorrence of ideological conformity. There is no role in this multivalent movement for one group to set the tune, and that baffles and disturbs the elite, who are behaving like a bunch of ageing rock fans being prised away from their dusty CD collections.

The problem is that a political class raised on vinyl and vanguardism is only now attempting to understand a political generation that has had its Spotify moment. Technology has enabled kinds of social change that can respond in a global way to international crises, and its playlist of demands is uncomfortably broad. But on the edge of hearing, out of this cacophony of struggle, a terrifying harmony is beginning to emerge.