found here, a "standard" is "a musical piece of sufficiently enduring popularity to be made part of a permanent repertoire, esp. a popular song." Hence the idea of a "standard" applies to popular music and not to what is commonly known as "classical" music. Assuming the collocation, "sufficiently enduring popularity," means, in colloquial terms, that a song has lasted, at what point in its existence does it stop being a mere "song" and undergo the transformation into a "standard"? Is it a matter of sheer repetition or reiteration (re-recording)? And if, by widespread consensus, a song is considered a standard, does that mean it forever remains so, that it shall for all time be considered a "classic"? Alec Wilder, in his highly regarded American Popular Song: The Great Innovators, 1900-1950 (1972), shows how the vast majority of the songs considered standards were a consequence of the institutional forms of songwriting known as Tin Pan Alley, Broadway musical theater, and the Hollywood musical. Obviously this is yet another way that "popular" is distinguished from "classical" music (the latter played almost exclusively by professionals), that the standard is a consequence of a certain level of industrial organization that allowed for the manufacture and distribution of music stored in a durable medium: material artifacts (records and sheet music), and methods of dissemination (movies and radio). I therefore note that "storage," in the sense of a storehouse filled with stock, that is, a repertory or archive (repertoire), is essential to the idea of a "standard." The latter practice--the publication of sheet music--also helped bolster the idea of "popular" music, since the printing of sheet music enabled songs to be sold to amateur musicians (beginning in the late nineteenth century, largely comprised of fledgling pianists) in private homes. The publication of sheet music also allowed for the formation of the aforementioned archive, since there could be no such archive without printed music.
Hence the rise of the "song plugger." Song pluggers occupied a curious niche; they were pianists and singers who earned their income selling songs in order to promote the purchase of sheet music, demonstrating the virtues of an individual song rather like a door-to-door vacuum cleaner salesman demonstrated the virtues of the latest home-cleaning appliance. However, the singers who first recorded the songs that became standards were not considered amateurs, but professionals; they were not song pluggers. That is, in order for a song to become a standard, it almost certainly had to be recorded by one of the dominant singers or performers on Broadway and in Hollywood during the period Wilder identifies, 1900-1950: Fred Astaire, Ethel Merman, Judy Garland, and Bing Crosby, to name just a few. Many of the songs that became standards were written especially for these highly-regarded singers who were appearing on Broadway and in Hollywood musicals. Most often, standards became more or less identified with the singer that introduced them--they became, as it were, "validated." Hence the standard became a sort of shibboleth: a required performative test, the purpose of which was to determine the authenticity of the vocalist. The standard became a means of including and excluding authentic performers: in order to demonstrate your "mettle," you had to perform a standard. Every singer "worth his (or her) salt," as they used to say, had to record a standard. Paradoxically, although the very idea of the standard required the existence of printed music, individual performance was valued over the strict adherence to the written composition.
According to Donald Clarke, in The Rise and Fall of Popular Music (Penguin, 1995), by 1950 or so standards were no longer originating in the places they had before (that is, in Tin Pan Alley, in Broadway and Hollywood musicals): "By the early 1950s, however, everything had changed. Blacks were doing their own thing in a new era, for labels created especially to sell to the black market; and good white songs were becoming scarce. The Berlins, Gershwins and the rest had died or retired, and the classic songs they had written could not be imitated" (366). Hence Clarke, among others, subscribes to the view that the decline of Tin Pan Alley coincided with the rise of rock & roll. Perhaps he's right.
As a postmodern art form privileging recording (engineering) over live performance, rock & roll was popular music largely written and performed by amateurs, not professionals, operating outside of the traditional music writing and publishing institutions, making records for small labels that were sold to niche (often regional) audiences. The decline of Broadway and Hollywood musicals, ensemble forms, coincided with the rise of the singer-songwriter, which championed individuality. There were, comparatively speaking, fewer new musicals created in the 1950s than in the preceding decades. One way to understand the rise of the singer-songwriter is to understand that they working outside established institutions such as the Broadway and Hollywood musical. When Elvis (for instance), decided to record songs written by Otis Blackwell (for instance), the cultural continuity suggested by the "standard" was broken. Rock & roll, music played by amateurs (Elvis had no professional training) thus represented a break in established traditions. It should therefore be no surprise that the first important record consisting entirely of standards emerged during a period of nostalgia, the early 1970s. That record was Harry Nilsson's A Little Touch of Schmilsson in the Night (1973), released during the period which saw the popularity of "oldies" groups such as Sha Na Na and nostalgic films such as American Graffiti (1973). Contemporary records such as Rod Stewart's "Great American Songbook" series represent a continuation of this trend in what is now the decline of the rock era.