Like eating veal or watching Channel 5's surveillance show Cheaters, listening to Eminem is a guilty pleasure. He is audibly the most exciting, original hip-hop artist to emerge in years, marrying commercial hooks to a breathtaking lyrical dexterity.
The problem lies in squaring those lyrics with your enjoyment of his records. Eminem's own defence, that all the stuff about rape and murdering homosexuals is just a laugh, doesn't cut much ice, mainly because his lyrics are less funny than disturbing.
A more convincing line suggests Eminem's music is a sort of existential scream, a darkly satirical howl at the injustice of American society and the hypocrisy of fame. The Marshall Mathers LP is a hip-hop equivalent of Brass Eye, complete with attendant controversy.
That conscience-salving theory was damaged by the release of Devil's Night, the debut album by D12 - Eminem plus five Detroit rappers he performed with before his success. Devil's Night has the nastiness of his solo work, offering gags about sex with the handicapped, eating infant corpses and breaking wind, without the vindicatory angst.
If you buy the Eminem-as-bleak-existential-satirist line, hearing D12 is rather like discovering Chris Morris is a nom de plume for Roy "Chubby" Brown.
Just as Eminem's appearance on Devil's Night ensured massive sales, so his presence tonight guarantees a packed house, including a number of parent-chaperoned pre-pubescents. Perhaps inevitably, D12 take the stage one at a time.
The audience howl their approval of each rapper's arrival with the stoicism of people who have gone on a date and discovered the object of their affections has turned up with five friends. Besides Eminem, D12's best MC is the drawling Bizarre. Despite an introduction promising "the sickest motherfucker in the world", Bizarre turns out to be an extremely fat man shuffling around in a shower cap.
When Eminem finally appears during Shit on You, pandemonium breaks out in the crowd. His wiry, hyperactive presence has an equally energising effect on the show, which suddenly develops a frantic, goofy pace. D12 stagedive, pretend to take drugs and play-fight. During Purple Pills, a roadie staggers about the stage dressed as a giant E.
It's hardly subtle, but it's entertaining enough to detract from the appalling sound, which muffles tracks such as Fight Music to shouty incomprehension. That in itself has a strange side-effect: for perhaps the first time, the debate about Eminem's lyrics becomes entirely academic.
