You may know Pearl Jam for their commercial success. Each of their releases has gone platinum several times over, and No Code (Epic) is the fastest-selling album of the year. You may know them for their "issues". Eddie Vedder, their lead singer and the reluctant voice of a generation (ie Generation X), squeezes his musical endeavours between battles for animal rights, the environment, housing for the homeless, and cheaper concert tickets, to name but a few of his favourite causes.

It's more likely, however, that you'll know Pearl Jam as the band Kurt Cobain loved to hate. Convinced that angst-ridden punk-metal belonged to him and him alone, he excoriated his Seattle rivals as sold-out, hyped- up fakers, and the British music press followed suit. In response, Pearl Jam have done all they can to be as "real" and unhyped as possible, short of actually banning people from buying their records.

This attitude would seem to damage one's chances of putting on an entertaining show. If you're determined to be real, you can't be doing with the showbiz artifice of high-concept staging or choreography, let alone putting on clothes more stylish than those you'd wear to creosote the garden shed. But at Wembley Arena on Monday, Pearl Jam's first British concert in three years was an entertaining show against the odds. There were just enough concessions to theatre - a giant mirrorball, a strobe that fired flickering shadows onto the backdrop - and while the once-acrobatic Vedder confined his movements to a shake of the fringe, his bandmates took it in turns to jump and spin like the Who fans they are.

It made for an invigorating couple of hours. By the end, however, one is left none the wiser as to what the songs are driving at, or what it is that drives the band. Musically they never venture beyond the scrabbling, scruffy guitars of the fast numbers, or the Neil Young-influenced folksiness of the slow ones. Lyrically, they are self-indulgently vague. A case in point is the most furious song they played on Monday, "Spin the Black Circle". The band scrub at their guitars, and Vedder screams until he tears his throat to ribbons. And what is the subject of the song? What has provoked this soul-wrenching anguish? His preference for vinyl over CDs. To misquote The Wild One: "What are you getting in a tizzy about, Eddie?" "What've you got?"

The problem may be that grunge is the music of inarticulacy, for and by people who want to say that they don't know what they want to say. That's all very valid and rock'n'roll, of course, and it served as a healthy, unpretentious kick against the meathead metal of the late Eighties, with its attitude of "bring me my hairspray, bring me my spandex, bring me my women - in that order". Four albums down the line, however, Pearl Jam and the rest of the post-metal guitar bands are starting to look as irrelevant as the motley crews they succeeded.

The Beautiful South are similarly problematic. 1994's compilation, Carry On Up the Charts (Go! Discs), is one of the top 20 best-selling British albums ever, and the new Blue is the Colour has knocked Simply Red off the No 1 slot - and yet the band remain the least pop starry of pop stars. They never show their faces on their record sleeves (once you've seen them in the flesh, you'll know why), and as they have three, interchangeable lead singers, they sidestep the possibility of a cult of personality.

At the Shepherd's Bush Empire on Tuesday, one songwriter, David Rotheray, stayed in the background, letting delicate, trembling chords leak from his guitar. The other writer, the hulking Paul Heaton, was off-stage for half of the songs, and when he was on it, he was either deadpan, dead drunk or just dead boring. He crafts lyrics that overflow with his love of wordplay, and his hatred of just about everything else, including himself - but he has to read them from a prompt sheet on a music stand. He seems intent on undermining every beauty of The Beautiful South. Staggering around in sagging jeans, a fleecy Russian hat, and a voluminous red cagoule, he followed a moving, soulful rendition of "Blackbird on the Wire" with a sarcastic: "Oh, I'm gettin' all dewy-eyed."

Maybe The Beautiful South would prefer it if the crowd ignored the musicians and focused on the melodies of their unmistakable, bittersweet songs - the Latin sway of "Have Fun"; the sea shanty, "One Last Love Song". In which case, give us one good reason why we shouldn't just forget them as a live act and listen to their records?

On Tuesday, the good reason was their support act, Beth Orton, a singer- songwriter from Norwich who has already made a name for herself by loaning her artlessly enchanting vocals to the Chemical Brothers and William Orbit. Rather than continuing down the most obvious, commercial road of dance music, however, this Giacometti gamine has done a U-turn and followed the sign marked "folk". Her debut album, Trailer Park (Heavenly), has its share of breakbeats, but on stage her raggle-taggle young band use nothing more high-tech than an electric piano. Her misty melancholic ballads are just as haunting either way.

The Beautiful South: Warrington Parr Hall (01925 634958), tonight; Leeds T&C (0113 280 0100), Mon; Glasgow Barrowland (0141 552 4601), Tues.