Womad, Charlton Park, Malmesbury

Womad's stated desire to leave its new home on Lord Suffolk's estate "in the condition in which we found it" will only have been met if the site always looks like the Somme in 1916. Steady rain has turned the rolling greenery to ankle-deep rivers of mud. But, in between, there is sunshine. There's also a dizzying array of music, proving that, in its 25th year, Womad has stayed true to pop's most radical, pleasurable promises of community and change.

In between Friday and Sunday's high-profile headliners, Peter Gabriel and Baaba Maal, it is the sparks of connection I feel watching less familiar acts that really matter. Friday's highlight is Maal's young Senegalese compatriots, the fiercely joyful reggae-rappers Daara J. And on Saturday, Tanzania's Zawose Family are a revelation. This is their first Womad visit since the deaths of guiding elders Hukwe and Charles, but the younger family members add to their legacy. Dressed in bright, traditional clothes, the men shake notes out of their thumb-pianos as they dance, while the women slap drums held between their thighs with dexterous, odd rhythms, and sing in full-blooded, hectoring harmonies. Despite a song called "Suffering", mourning their family and country's losses, they vibrantly counter the death images of Africa we're usually fed.

The Zawoses's local guitar sounds eerily like Appalachian banjo, and such moments of recognition multiply as I criss-cross the site. The Cape Verdean chanson singer Cesaria Evora is a big, stone-faced woman, saving expression for her sorrowful tenor voice, singing this Gallic soul music. And soon afterwards, America's soul treasure Candi Staton can be heard singing "Young Hearts Run Free", with ageless, blissful excitement. While Staton plays, the West Country folk singer Seth Lakeman is lamenting the brave, lost 1980s Cornish lifeboatmen of the Solomon Browne. Such local moments are special, but Lakeman is still callow.

The Imagined Village, an attempt to open English folk to modern, world influences by a collective including Billy Bragg and Eliza Carthy, is more promising. A swirling, English ceilidh, stitched together by electric guitar and Indian drums and angry lyrics about current rural life, has righteous fire. As when Arizona's Calexico, usually considered alt.country, emphasise their Latin side, making North America and southern Europe sound as exotic as Senegal. At Womad, boundaries blur.

CJ Chenier's zydeco band is pure, down-home bar-band pleasure, on the way to Saturday's headliner, Isaac Hayes. It is steadily raining by now, with promises of torrents to wash us away, and Hayes fails to read the mood, with typically slow-building selections. Only when "Soul Man" is followed by Hayes theatrically conducting in the wah-wah guitar of a majestic "Theme from Shaft" does everyone start smiling and dancing, and the rain cease to matter.

Sunday has two clear stars. The back-story of Tinariwen, one-time Tuareg rebels who now play desert blues, has left journalists over-excited (Marzoug are here with the same MO). More relevant is the way they take freely from, and refresh, black US blues, a triangular connection between Africa and the West heard all over this weekend. In blue and white robes matching the now clear sky, they at times play pure psychedelic blues, at others the talking Saharan kind, in which you can hear the US blues struggling to be born.

Portugal's fado singer Mariza's vampish black dress suggests a combination of 18th-century court, 1920s cabaret and 1930s movie star. And, singing Europe's most sinuously sensual music, she expresses it bodily: kneeling at the lip of the stage as she whispers, her voice like pure breath, then arching her back, eyes closed and fingers grasping at the force of her emotion, her voice now furiously powerful, yet utterly controlled. It is a theatrical, exotic spectacle, making the crowd hold its breath, before wild cheers. It lingers as I leave the best music festival I've seen.