It was like the payoff scene from Slumdog Millionaire: men and women dancing in Rio’s main railway station — gyrating streams of dancing commuters following the bands as they paraded in circles around the concourse. And the noise was sensational.

It’s music that holds the soul of this city — and specifically, it’s samba. The wonderful, lilting rhythms are everywhere: in the movements of the volleyball players on Copacabana beach; in the hand gestures of the coffee-drinkers in the city’s cafes; and in the free-flowing ebb and sway of Brazilian football.

Most of us come to our image of Rio through the verve of the Lenten Carnival. But in December, the city takes to the streets again for National Samba Day. I’d bought my ticket for something called the Samba Train, and was ready to take my seat and be serenaded by assorted musicians.

The train was meant to leave at 7pm, but by 7.20 showed no signs of it — and you couldn’t move so much as an eyebrow in my carriage; it felt like being packed into an overstuffed metal suitcase.

The nightlife guide to Rio

Beauty queens, samba and hangovers - Samantha Lyster experiences it all in Rio

• Where to samba in Rio

• Making friends in Rio's B&Bs

The finest Brazilian white sand island

Revel in the simple island life in idyllic Boipeba, where a tenner buys a feast in the local lobster shack

The smart guide to Sao Paulo

Brazil's largest city is too often overlooked in favour of Rio. Simon Warburton offers the low down

Related Links

• The nightlife guide to Rio

Men and women banged drums and tambourines, and every so often the entire carriage would rock with a rhythm bashed onto the ceiling or stamped on the floor. Then a rumour spread that we had boarded the wrong train: the correct one was on the opposite platform. There was a rush, then a crush — and, in less than a minute, 5,000 people had filled a train built for 500.

We waited for another half an hour, and finally we were off — on a 45-minute journey into the suburbs, where the samba festival was in full swing. As we pulled into the station, a river of human beings swirled before us, illuminated by the glow of light-bulb-lit stalls selling chicken and beer, lollipops and sausages.

I unpacked myself from the carriage and headed off into the noise. I’ve never seen so many smiling people in one place — people of all ages, somehow walking and dancing at the same time.

Samba has its roots in West Africa, and arrived with the dreadful cargo of four million slaves transported to South America — many more than ended up in the USA. For generations, its infectious rhythms were kept alive in the secret rituals of Candomblé, a religion that travelled across the Atlantic with the slaves.

For its believers, the drums became synonymous with dignity. Many Candomblé temples still thrive in the Rio favelas but, until as recently as the 1970s, their location had to be kept secret.

I visited such a temple on the outskirts of the city, and the service was a ferment of feverish samba. Adherents believe the music summons spirits: the spirits of courage, of peace and of celebration — and, most of all, the spirits of their ancestors. Everything about that Candomblé temple felt essentially African: the mannerisms of the preacher, the movements of the congregation — and the drumming, of course.

Rio is really two cities united by a single music, and Christ the Redeemer stands on the dividing line, gazing out over the white high-rises of Ipanema and Copacabana. If Christ were to turn around, he would face the favelas — miles of condensed streets and lost dogs, jagged corners to lie low in and the best graffiti in the world: torn grey faces wrapped around walls and under fly-overs alongside guns the size of cars.

On the day I arrived, a newspaper headline spilt a dark statistic: in the past year, 14% of males aged 15-19 had lost a friend to gun crime. I decided against taking the favelas tour promoted at my Ipanema-beach hotel. It sounded too much like blood money to me.

Times recommends

• Tuesday: the latest airport and flights news
• Wild Girls hit the Klosters slopes
• Red Sea: the complete guide