Nneka, ULU, London

A hip-hop star with more to say

Although one of the Mobo's less heralded awards has always been Best African Act, the 2009 winner, Nneka Egbuna, could well break the trend for underachievement set by previous recipients 9ice and Batman Samini.

Tonight's rambling performance should not detract from her undoubted potential. Nigeria-born Nneka beat off strong competition, particularly from the charismatic Amadou & Mariam and South Africa's cutting-edge funkmeister Mujava. The same month, she scraped the Top 20 with her urgent single "Heartbeat", from her second album, No Longer at Ease.

Its rootsy mix of reggae and hip-hop provides a more complimentary backing to her soulful vocals than the tinny trip-hop of Egbuna's 2005 debut, Victim of Truth, though out of the studio, she makes far less sense. Nneka sauntered on in gamine fashion, all baggy threads and easy slouch, in contrast to the earnest folk running the anti-Shell stall at the back.

She has a lot to say, as you might expect from a Nigerian performer with a half-German mother. Nneka moved to Hamburg aged 19 to pursue her singing career, while also studying anthropology.

Yet the 27-year-old reduced her message to platitudes about change and one love, delivered in a sluggish and unengaging monotone. There are rhetorical gems, as when she turns VIP into "Vagabonds in Power" or discusses how those with power refuse to change, whether "politicians, pastors, or... prostitutes", a joke lost on a crowd that lost the thread several clauses ago. The same problem occurs musically as Nneka drags out 12 numbers into an epic 90-minute set. Yet there are hints of a nimble musical brain and versatility as she moves from the warm croon of Randy Crawford to the smoky, lived-in quality of Macy Gray.

Her four-piece band come with all the chops to follow her moves, as when their regulation skank rhythm leaps to double time to meet the singer's increased intensity. Their pedestrian arrangements, though, sound brittle without the club-strength backing tracks that provide ballast, while the guitarist is prone to throwing in unnecessary rock solos. "Heartbeat" remains a highlight and Nneka shows herself adept at crisp hip-hop soul on "Death", with spoken interludes as sharp as rap. Intriguingly, the Latino rhythm of "VIP" suggests a female Manu Chao. She encores, disappointingly, with the Lenny Kravitz-style wig out of "Focus", something she has lacked for much of the evening.