With a very simple premise, rapper Ice-T – this film's presenter and co-director with Andy Baybutt – has created a very enjoyable and often fascinating movie. His purpose is to discuss rap and hip-hop with some of its biggest stars, as far as possible concentrating on the technical aspects of composition – the prosody of rap. He's not interested in the bling or the gangsta-ism, or even much in its actual history: simply the business of rap itself. Ice-T talks to Dr Dre, Eminem, Snoop Dogg and many more. Essentially, what results is a series of impromptu performances – by the pool, on street corners, in the studio. Some might feel that there is too much mutual male admiration. But the performances can be mesmerising: aggressive, defiant, toweringly incorrect, brutally offensive and brilliant: some stunning displays of linguistic dexterity. What is extraordinary is that the rapper is the last breed of professional writer who composes longhand, pen on paper – or maybe, when inspiration strikes, on the back of the hand. There are no laptops. We see them write out verses in very neat handwriting on yellow legal pads. Rapping grew out of macho battles, and yet the consensus here is that it will only get the respect given to jazz and blues when its stars are more extravagantly nice to each other. Will that ever be possible?