New York hip-hopper Nas and Jamaican reggaeman Damian Jr Gong Marley – son of Bob – should make a very odd couple. They look completely different: Nas in crisp white T-shirt and a modicum of bling, and the dreadlocked Marley in reggae-regulation combats. And yet, by tracing the African roots their music shares, they have emerged as one of pop's most extraordinary and exciting collaborations. Their very late entrance in Manchester is marked by a stampede to the front.

The two musicians interweave and complement each other in a way that is almost uncanny. Nasir Jones remains a top-notch rapper, able to fire off compulsive rhymes without pausing for breath. Marley's singing is more mournful than his father's – and by bringing hip-hop elements to a classic reggae delivery, he has found his own voice.

Tracks from their album Distant Relatives (with which they are raising funds for African schools) are a dizzying fusion of reggae and hip-hop, and talk about genocide and revolution. In the sublime Tribes at War, Marley's cry of "Everyone deserves to earn, every child deserves to learn" is powerfully haunting.

The pair then part company to perform tracks from their own back catalogues: Nas for hip-hop classics such as Hip Hop Is Dead, and a storming If I Ruled the World; and Marley for 2005's Welcome to Jamrock, and a musical nod or two to his father. But the electricity when they are on stage together is remarkable. The atmosphere is perhaps similar to Bob Marley's epochal 1975 Lyceum gig: diverse cultures coming together to celebrate the shock of something different and wonderful.