Warning is an album by a heavy metal band.
 Appraising the concept in Christgau's Record Guide: Rock Albums of the Seventies (1981), Robert Christgau said most "are profit-taking recaps marred by sound and format inappropriate to phonographic reproduction (you can't put sights, smells, or fellowship on audio tape)
== Types of album ==The contents of the album are usually recorded in a studio or live in concert, though may be recorded in other locations, such as at home (as with JJ Cale's Okie, Beck's Odelay, David Gray's White Ladder, and others), in the field  as with early Blues recordings, in prison, or with a mobile recording unit such as the Rolling Stones Mobile Studio

