A superhero's powers are set free by his costume. The comic-book collaboration MadVillain – west-coast producer Madlib and villainous NYC rapper MF Doom – would be nothing without Doom's ever-present metal mask. He wears the mask on stage and refuses to be photographed without it: a full-face crown that, by hiding his real identity, gives him reign over a whole kingdom of selves. Doom, real name Daniel Dumile, is a chronically split personality: his aliases range from positive rapper Z-Love X to King Geedorah, a giant gold-plated lizard. When one reporter asked Doom about King Geedorah, he hung up; when the reporter called back, 'Geedorah' answered the phone. Doom's production, which he usually handles himself, exhibits the same unpredictability.

This new partnership with Madlib is a bid for commercial stability, and at first listen it's a good match. Madlib's beats, crafted with a jazzman's careful carelessness, fit well with Doom's slurred delivery and cultivated torpor.

The sloth is an act – the duo move through 22 tracks in 46 minutes without a single chorus. There's no time for repetition: Madlib's harmonicas, xylophones and church organs are busy slugging it out with Doom's alcoholics, supervillains and B-movie episodes. In between the stronger moments instrumentals and guest rappers slacken the pace, but MF Doom's raw brilliance always reinvigorates the track. His rhymes miss beats, drop into the middle of the next line, work their way through whole verses. The densely telegraphic lyrics almost always reward closer inspection. When Doom raps, 'The smoke clears, you can see the sky again/ There will be the chopped-off heads of Leviathan,' you think he's bragging about the impact of MadVillain – until he mentions 'Manhattan warmongers'; the whole verse is cast in a different light.

Doom has put out five albums in the past four years; all have shown the same half-polished promise. Here, the stand-out tracks – 'Money Folder', 'Figaro', 'Great Day' – again demonstrate a unique lyrical talent that has everything except calm. If he manages to find the right partner to ground and focus his style – Madlib isn't quite businesslike enough – Doom will be able to stake a clearer claim as 'the best MC with no chain you ever heard'.

related artists Madlib, Madvillain