Rock: What's Irish for fruity-voiced?

The Divine Comedy Brixton Academy, SW9 John Cale Royal Festival Hall, SE1

"I love being a pop star," said Neil Hannon with a shy smirk before his encore last Saturday. "It's great fun. Absolutely insane. I should not be here." And in a way, he was right. He shouldn't have been there. The Divine Comedy (Hannon, plus whichever other musicians he requires at the time) were due to play a small warm-up show before setting off on tour as Robbie Williams's support act. Such was the demand for tickets, though, that the venue grew from "the poncey little Shepherd's Bush Empire" to the Brixton Academy, and the intimate dress rehearsal swelled into a major rock gig with all the trimmings: spinning spotlights, an acoustic set, a guest actor - Dexter Fletcher - doing a Phil Daniels, and 4,500 fans who roared along to the latest single so lustily that to look at them, you'd never imagine they were accompanying a pint-sized dandy in a three-piece suit on an ironic tribute to a coach firm.

It was a heart-warming evening, reminiscent of seeing Bjork at Wembley Arena and marvelling at a world that could turn someone so determinedly loopy into a bestseller. More English than most Englishmen - as Irish literary types often are - Hannon has adopted a top-of-the-fops persona and a voice which is fruitier and plummier than Leslie Phillips in a jam factory. He also has the face of a self-satisfied budgie and the physique of a Thunderbirds puppet. He is not your average Smash Hits pin-up.

How he managed to sneak up to this level of success, then, is a matter of debate. True, he has had his share of publicity, but most of it has concentrated on his Father Ted music, and he still hasn't dispelled his reputation as a novelty act. Not that he has tried very hard. From "Frog Princess" to "National Express", Hannon has kept writing so-called humorous songs. And in pop music, comedy is rarely divine. Sometimes the jokes and the emotion pull in the same direction: Pulp's "Common People" is both as hilarious and as impassioned as a pop song can be. But usually a pop/comedy crossover means a potentially moving song being undermined by a snide punchline: a mean- spirited pastiche by someone who believes himself to be too clever to be sincere in such an elementary genre. Besides, it's never very funny.

Tempting as it may be to dismiss Hannon on these grounds, he is none the less making some of today's most wonderful records. He can fit together his carefully chosen words and gorgeous orchestral music in to shapes which his peers couldn't imagine, but anyone can whistle - Burt Bacharach's subtly complicated melodies sung by Noel Coward and recorded in Phil Spector's best pop-symphonic style. To see these gems performed by Hannon and six sensational musicians, all wearing suits, is nothing short of fabulous.

Again and again, though, Saturday's most magnificent moments came when Hannon wasn't undermining himself with cheap bathos - that is, when he revealed the man behind the waistcoat. "Sunrise" and "Generation Sex", in particular, glow with wit and fury in equal measure. On these songs Hannon engages with subject matter that few other pop stars would go near. Indeed, he engages with subject matter, full stop, and there aren't many pop stars who do even that.

In a career of over 30 years, John Cale has been a record producer, a movie soundtracker, an avant-garde composer and a conductor. And he is still best known for making his viola sound like a dentist's drill on the first two Velvet Underground albums. Now, at 56, he's taking stock. In the past month, there has been a compilation album (you could hardly call it a Greatest Hits), a BBC2 profile and an autobiography, What's Welsh For Zen, a book which should have been, but sadly wasn't, subtitled "Lou Reed is a Shit". And on Thursday, he played songs drawn from his whole career - although with no screeching viola and nothing by the Velvets.

This was Cale Unplugged: clomping the same chords over and over on the piano, and bashing out repetitive folk songs on an acoustic guitar. Meanwhile, the other two-thirds of the John Cale Trio, Lance Doss and Mark Deffenbaugh, sat in among a heap of acoustic instruments, from mandolin and banjo to harmonica and Jews harp.

Cale strains his words through gritted teeth like Bob Dylan after a stint in a male voice choir, but stripped-down singer-songwriter is his least convincing guise. It's not that the songs are bad, it's just that you wouldn't bother with them if you didn't know their author's history. And paradoxically, when you do know his history, they can only seem monotonous and uninspired compared with other material he's had a hand in.

Cale is best when he's throwing a creative spanner in other people's work. A central theme of What's Welsh For Zen is that he has always been a collaborator - even the autobiography is co-written - and Thursday's highlights were Leonard Cohen's "Hallelujah", "Style It Takes", which Cale co-wrote with Lou Reed, and his infamous party-piece, a macabre resetting of "Heartbreak Hotel". It begins as a sombre, Nick Cave-style lament and builds to a spine-chilling climax with a demented squeal from Cale and a thunderclap from the piano. In short, the madder Cale's music is, the better it is. He should leave the busking to Reed, and take to heart the words he sang at the start of the show, penned by another of his collaborators: "do not go gentle into that good night".