In The Gambia you make friends quickly. Jeroen, the Dutch lad who has been my friend for precisely fifteen minutes, is pouring out his heart to me over the breakfast table in the garden at our hotel. A skinny Gambian kitten, which has been our friend for precisely two minutes and already feels confident enough to help itself to cheese from our plates, leaps, dusty-footed, onto his lap, but Jeroen is too preoccupied to shoo it away.

"I can't decide about Awa's invitation," he explains. Awa is the young Gambian woman he met a couple of days ago on this, his first visit to West Africa. They are already the best of friends. "Her brother's wife has a new baby. Tomorrow the family is having a big party in their compound. And I'm invited. It's bound to be amazing, it'll be a real family celebration, with a chance to hear real Gambian music, but I don't know what to say. I'd love to go, but people keep telling me that if I do, the family might expect me to pay for the musicians, the food, and everything, just because I'm a toubab..."

I smile sympathetically. Toubab is the name that West Africans use for whites. It's not derogatory and it's applied indiscriminately. Children bleat "Toubab, toubab!" at any glimpse of a white face in the street and if you're white, adults will refer to you as "the toubab" long after they know your name, or that you're English, or American, or an architect, or whatever else you might be - you're white, you're a toubab, that is your defining feature. And all toubabs are assumed to share certain attributes and inclinations, including, often, an ability and willingness to pay for parties - until you politely explain otherwise.

"Be honest with her," I say. "Tell her how honoured you are to be invited and ask her frankly what kind of present her family might expect. Tell her you'd like to bring something, but you can't afford much. But whatever you do, go! You'll have the time of your life!"

In The Gambia, a naming ceremony is held exactly one week after a baby is born. The new mother has a week to recover from the birth and in this time her baby does not leave her home. Then, on the seventh day, everybody gathers for a knees-up. The proud mother, hair newly braided, is dressed in her most elaborate boubou and her most fabulous jewellery, and generally treated like a queen. The baby is named, and the whole family and all their friends, if not the entire village, tuck into a feast. Crucially, a band of jalis, master musicians, are invited along to play, and everybody takes turns to dance the high-stepping, stomping solos that elicit shrieks and applause the faster they go.

When, on a still, hot evening, you hear the sound of drums reverberating in the distance, there's a good chance that a week-old baby is being welcomed into the world. As a visitor to the country, an invitation to such an event is not something to be taken lightly. If you have any interest in traditional music, this is where you'll find the real thing.

Traditional music plays a pivotal role in West African life. In The Gambia and its larger neighbour Senegal, which shares its cultural heritage, every human event - be it a birth, a coming of age, a marriage or a death - is marked by drumming and dancing. Storytelling, music and dance are intricately connected. The jalis are the custodians of folk history, which they convey through rhythm and song, and the dances associated with their music are an expression both of individuality and of community solidarity.

It's a tradition that resonates far beyond African shores. As Baba Ishangi, an Africology expert from Brooklyn, New York, puts it: "The principles of West African music and dance inhabit the collective cultural memory of African descendants throughout the diaspora. Hear Senegambian rhythms and you hear the foundations of music by Western stars like Aaliyah, Michael Jackson and BB King. See a Fulani dance and you understand exactly where break-dancing comes from."

New arrivals at Banjul International Airport, gateway to The Gambia, are bombarded with music from the moment they set foot off the plane: chances are there'll be a grinning drum- and dance troupe among the welcome committee. The tourist hotels make a point of inviting musicians, especially solo kora players, to entertain evening diners. The kora is the 21-string harp of the Manding people, of which the Gambian Mandinkas are a branch. Kora songs, lilting and ethereal, are The Gambia's most distinctive folk tradition. Hotel sessions are a welcome, if tame, introduction to the Senegambian live music scene. But it doesn't take too much adventuring to track down a taste of grass roots music - just head for a local night club, or a music bar, or, better still (as my friend Jeroen discovered) wangle an invitation to a private party.

Making sure you're in Africa during a major festival is an excellent way to tap straight into the music scene. The biennial International Roots Festival in The Gambia is an unmissable musical showcase. Anyone planning a visit to West Africa around this event should prepare to witness more noise, colour and sheer energy than they ever thought possible. The festival runs over nine days and includes stage shows, visits to heritage sites, a cultural pilgrimage and a regatta complete with greasy pole wrestling.

Underpinning all the events is an exploration, and celebration, of The Gambia's rich cultural diversity. The uniting theme is music - bands play at every event, from village troupes beating out rhythms on bamboo clappers to top-ranking superstars packing out the country's biggest sports stadium. Historically, Gambian musicians have always had a raw deal when it comes to making a mark on the international music scene. The country has the most rudimentary of infrastructures for professional musicians. Copyright is barely regulated, if at all, so that profits from any recordings that are made are swiftly eaten away by unscrupulous pirating. Some guidebooks unthinkingly perpetuate this situation by directing tourists to shops where you can get a recording taped for little more than the price of a blank cassette.

Most Gambian musicians have to scrape together a living from tips for live appearances or from teaching. Lamin Kuyateh, a jali who makes and sells instruments in Banjul's Albert Market, says it's difficult, as a consequence, to put your finger on who are the greatest Gambian musicians. "Very few Gambian musicians are well known outside this country," he explains. "There are many excellent musicians whose music is never heard outside their own compound."

To spread the word further, Gambian musicians head for Senegal - which takes cash and commitment. Dakar, the capital, is the nerve centre of the Senegambian music scene. This hot, fast, urban jumble of crumbling French colonial buildings and towering modern corporate headquarters swaggers to the rhythm of the music that was born here: mbalax. The city's soundtrack seeps out of the roadside stalls, the bars and the bush taxis: rippling tama (talking drums), pounding sabar (tall drums) and the nasal keening of the gawlis - traditional singers of the Wolof people. Everybody who is anybody in Senegambian music either hails from Dakar or comes here to perform and record. The Dakarois recording industry is, in West African terms, a sophisticated machine. For visiting music fans, the city is one of the best places to catch live gigs.

The biggest names in Senegalese music are familiar to Western audiences, but the sets they play on home turf are different. There's nothing to beat the experience of rubbing shoulders with a delirious, sweaty crowd, cool beer in hand, starry sky overhead. If you want to see a major celebrity like Youssou N'Dour, all you have to do is head down to his club, Thiossane - he and his band play there several nights a week, into the small hours, whenever he's in town.

Though better resourced than Gambians, Senegalese musicians still have to struggle against adversity to make it in a competitive arena. Their passion breeds resourcefulness. Ismaà«l Lô, the son of a Senegalese civil servant, was not born into poverty, but his route to the top wasn't easy. He built his first guitar from a cooking oil can and he taught himself to play guitar and harmonica simultaneously by nailing his harmonica to the wall. Now he's known as the African Bob Dylan, both as a musician and as a poet. Optimism in the face of the harshness of African life floods across in his lyrics. He remarks simply: "I speak of racism, poverty, famine and the relationships between people".

It is the unassailable warmth of the Senegambian people that makes visitors want to return to the region time and time again, just like Jeroen, whose participation in Awa's family's naming ceremony left him on a triumphant high. He's now such good friends with the drum band that played there that they've made him an honorary member. "They taught me a Wolof proverb," he tells me. "‘You can't beat a drum and scratch your head at the same time.' I tell you, when you're playing that music, you can't think about doing anything else. It takes you over. You discover a whole new side to yourself."

Dip a toe in this ocean of musical talent, or, better still, jump in with both feet, and you too might find your life changed forever.