The Great American Songbook, also known as "American Standards", is the canon of the most important and influential American popular songs and jazz standards from the early 20th century. Although several collections of music have been published under the title, it does not refer to any actual book or specific list of songs, but to a loosely defined set including the most popular and enduring songs from the 1920s to the 1950s that were created for Broadway theatre, musical theatre, and Hollywood musical film. They have been recorded and performed by a large number and wide range of singers, instrumental bands, and jazz musicians. The Songbook comprises standards by George Gershwin, Cole Porter, and Irving Berlin, and also Jerome Kern, Harold Arlen, Johnny Mercer, Richard Rodgers, and others.