ROCK / New tricks from pop's old dogs

ALI CAMPBELL is almost dead from the waist up. The UB40 singer does rock perceptibly on his ankles, and chop stiff-armed at a guitar for a few songs, but his box-jacketed chest and jutting jaw barely move as they send that unmistakable whine across the Cardiff International Arena. Behind his back, the other nine musicians do some modest formation dance steps; but they too are slaves to UB40's relentlessly chugging rhythm.

UB40 give new meaning to 'rock-steady'. This is the 15th year of their near-residence on Radio 1, from 'Food for Thought' in 1980 to last year's No 1 'Can't Help Falling in Love', ubiquitous despite being the theme song to the embarrassing Sliver. They're astute too. In 1983, a UB40 single failed to chart for the first time and the Midlands agit-reggae scene that spawned them was fading. They just dropped the songs about unemployment and learnt the words to Neil Diamond's 'Red Red Wine', which went to No 1 and began an apparently infinite series of gently reggaefied MOR covers.

For the first 15 minutes, they threaten to be as adventurous as a metronome. A rhythm- guitar itch starts, then settles in for the night on a bouncy bed of keyboards and percussion. Ali Campbell's constricted white- rasta voice strains, enunciating every word the same nasal way. The band stand in three ranks - what someone once called their 4-4-2 formation - and look set to keep this up for the full 90 minutes. Their polite pop translation of reggae seems intent on ignoring all the form's recent innovations, from Shabba Ranks's furious ragga chat to the Orb's cosmic, floor-shaking dub.

But the floor is shaking - from the front right to the back, people are dancing. More people are dancing more busily than at a rave. Whole families are singing all the words to all the songs, cheering every small instrumental flourish, shouting 'brilliant' at each other.

Why? Well, someone must have bought all those singles. And Campbell's chat about Jamaica goes down well in a sleety mid-January. But more importantly and surprisingly, UB40 are starting to mess around. They drop the 4-4-2 for a bit of total football, swapping roles and instruments, loosening and fattening their sound. Campbell gives the microphone to support singer Bitty McClean for 10 minutes of throaty toasting. When Campbell returns, his voice is warped through an echo box into strange fuzzy shapes. People cheer. 'Red Red Wine' gets introduced Spinal Tap-style, as something 'a bit more jazzy'. People scream.

And UB40's musical trademarks, far from becoming unbearable, begin to seem intelligent. Their four horn players, spotlit centre stage, pep up even the more laboured songs, with Motown-style swinging salvos. Little percussive patters relieve the repetition of the backbeat. There are no long- winded solos. The whole package - essentially happy music, sad lyrics - may be the oldest pop trick in the book, but it's a good one, and no one ever criticised The Smiths for using it.

Birmingham NEC, tonight, Mon, Tues; Edinburgh Ingliston Auditorium, Fri; Whitley Bay Ice Rink, Sat & Sun; Sheffield Arena, 18 Jan; Manchester G-Mex, 061-832 9000, 19 Jan; Wembley Arena, 22-23 Jan. All shows bar Manchester sold out.