Not all jazz standards were written by jazz composers. Songs included in major fake book publications (sheet music collections of popular tunes) and jazz reference works offer a rough guide to which songs are considered standards.
There is no definitive list of jazz standards, and the list of songs deemed to be standards changes over time. Jazz standards are musical compositions which are an important part of the musical repertoire of jazz musicians, in that they are widely known, performed, and recorded by jazz musicians, and widely known by listeners. More generally, the term “standard” can be applied to any popular song that has become very widely known within mainstream culture. The most popular and enduring songs from this style of music are known as pop standards or (where relevant) American standards. Allmusic defines traditional pop as “post-big band and pre-rock & roll pop music.” This definition is disputed by many scholars, however, as many of the most enduring and popular standards predate World War II, as for example most of the work of Cole Porter and George and Ira Gershwin - and in some cases, as with Irving Berlin and Jerome Kern, even World War I. Traditional/classic pop music is generally regarded as having existed between the mid-1940s and mid-1950s.