Plan B, Roundhouse, London<br/>Tomorrow, in a Year, Barbican, London

The golden age of pop- as-theatrical-narrative, as exemplified by David Bowie's Ziggy Stardust and The Who's Tommy, ended some three decades ago, but there's life in the greasepainted corpse yet.

We've already had a ballet from Damon Albarn and an opera from Rufus Wainwright, suggesting that rock is entering one of its intermittent phases of imperial decadence.

And now, in one of the more startling turnarounds in recent history, Forest Gate's Ben Drew, aka rapper Plan B, has ditched the grim urban underworld of night buses and knife crime he depicted on his debut album Who Needs Actions When You Got Words – his Plan A, if you will – and invented a fictional soul singer persona whose story, encompassing a false accusation of rape, a prison sentence and a murder, is recounted to a nouveau-Motown backbeat on the chart-topping album The Defamation of Strickland Banks.

There will, inevitably, be those who look at Drew's slick new image and hear his commercial new sound and cry "sell out", but for all anyone knows, maybe the hoodie-wearing survivalist of B's first album was a character too. For the rest of us, it's an absolute joy, one of the albums of the year, whose absence from the Mercury shortlist is further proof that the entire panel should be taken outside and shot.

Whenever a rough-looking young lad puts on a suit, it invariably goes one of four ways: nightclub bouncer, junior bank clerk, the bridegroom or the defendant. Ben Drew, however, scrubs up nicely. His aunties must nip his chubby cheeks with pride.

He may start tonight in a waistcoat, shirt and tie, the slightly naff gold chain across his collar betraying his edge-of-Essex origins, but for the first two songs his body language is still that of a rapper. Then, after a brief announcement – "Ladies and gentlemen, I would like to introduce .... Mr Strickland Banks!" – he slips into his suit jacket, and into character.

If The Defamation has a Chandler-esque pulp fiction/film noir feel, right down to the obligatory femme fatale, it's echoed visually by spinning newspaper headlines and black and white footage of an old-school boxing gym, but the songs are presented out of sequence, asking to be appreciated as discrete entities.

The first surprise is that Drew himself is an effortlessly confident showman, with no qualms about shouting "Take me to the bridge!" just like JB or getting those "coloured girls" to go doo-doo-doo like Lou. The second is that he can sing like an angel. There's no way a voice like this should be coming out of a face like that, but with no recourse to Autotune he hits every note, bang on the money.

Only a couple of relics from B's first incarnation survive, one of them the Gary Puckett-pilfering "Charmaine", a cautionary jailbait tale of an encounter with a girl whose "ass is tight and her breasts are bloody enormous", but turns out – too late – to be 14. If that misdemeanour were added to Strickland Banks's crimes, he would never see parole.

In complete contrast, when I heard that the Swedish electro-pop oddballs The Knife had written an entire "electro opera" on Charles Darwin, it barely raised a flicker of the brow. Tomorrow, in a Year is exactly the sort of project you'd expect from Olof Dreijer and his sister Karin Dreijer Andersson. The Knife are familiar to millions, albeit indirectly, via their song "Heartbeats", as sung by Jose Gonzalez, while Karin's side project, Fever Ray, are now popular enough to fill Brixton. Consequently, they have the wherewithal to stage something like this, though they themselves appear to be absent. I half-expected to spot the eccentric duo lurking in the wings, perhaps disguised by giant dodo beaks.

Darwin initially trained, somewhat reluctantly, as a cleric before switching to sciences. Some of that God-fearing superstition stayed with him during his voyages on the Beagle, and the world-changing implications of his findings regarding the taxonomical tree of life left him traumatised and conflicted. The realisation that an organism's appearance of being "designed" does not entail a designer had the result, according to Alan Desmond and Jane Moore's biography, that "a third of his working life was spent doubled up, trembling, vomiting and dowsing himself in icy water".

Every new discovery was the opposite of a joyful eureka moment for Darwin, and Tomorrow, in a Year – staged in collaboration with the Danish troupe Hotel Pro Forma – captures his feelings of unfolding dread. The plot is pushed along by an unsettlingly demonic prima donna who looks like Glenn Close, although, in compensation, there's a beautiful blonde ballerina in a Sixties dress who looks like Elke Sommer. The style is uncompromisingly modern and semi-abstract, the dancers acting out tableaux representing natural selection and mutation. It largely works, though overuse of a laser pointer (to trace the outline of the white cliffs of Dover, for example) can be grating.

The Knife's score, assisted by Planningtorock and Mt Sims, is reminiscent of Scott Walker and Ryuichi Sakamoto and treads a line between beauty and foreboding, although there's tittering when a rave beat kicks in and a dancer begins to body-pop. Finally, something resembling a normal Knife song pipes up, and the thin lady sings. The moral of the story of Darwin – and that of the Knife themselves – would appear to be as counterintuitive as the naturalist's own findings: if you want something done, ask a daydreamer.

Next Week:

Simon sneaks into the secret launch of Manic Street Preachers' 10th album, Postcards from a Young Man