text: Rob Reiner procured $60,000 from Marble Arch Productions to write a screenplay with McKean, Guest and Shearer, based on the Spinal Tap characters. They realized after a few days of writing that no script could capture the kind of movie they wanted to make, so they decided instead to shoot a short demo of the proposed film. They shopped the demo around to various studios but had no takers, until television writer-producer Norman Lear decided to back the project, providing them with a budget of 2 million dollars.
  Virtually all dialogue in the film is improvised. Actors were given outlines indicating where scenes would begin and end and character information necessary to avoid contradictions, but everything else came from the actors. As often as possible, the first take was used in the film, to capture natural reactions. Reiner wanted to list the entire cast as writers on the film to acknowledge their contributions, but the Writers' Guild objected, and so only he, Guest, McKean, and Shearer received writing credit.
  Veteran documentary cameraman Peter Smokler worked as cinematographer on the film. Smokler had great instincts for camera placement on set, according to Reiner, and is responsible for the film's handheld cinéma vérité style—although the cinematographer did not understand what was supposed to be funny about the movie. With Smokler behind the camera, the film was shot not as a feature film, but as a documentary, without a script or traditional shooting schedule. So much footage was filmed (over 100 hours) that it eventually required three editors to complete the film.