Ever since Louis Armstrong introduced virtuoso-quality improvisation to the world of jazz, there has been dissent in the jazz community about whether the music should emphasize melodic accessibility, and the artistic merits of music that does so wholeheartedly. Jazz has a well-established custom of using pop standards as jumping-off points for lengthy improvisations, satisfying jazz lovers and purists who appreciate the unpredictability and constant chance-taking. However, ever since the big-band era, there has also been a long-standing tradition of Jazz-Pop -- music that retains the melodic and rhythmically swinging qualities of jazz (as well as the basic chordal harmonies), but which (like pop) concentrates first and foremost on memorable melodies, usually with little to no improvisation.
In jazz's early days, dance orchestras began to adopt swing rhythms to keep in step with audience tastes. As the big band era wore on, most groups fell into one of two categories: sweet bands, which retained at least a lightly swinging feel but prized melody above all else, and hot bands, which were distinguished by greater solo improvisation, rhythmic drive, and blues feeling. Sweet bands helped pave the way for the rise of pop singers like Frank Sinatra, Tony Bennett, and Mel Tormé, who were at the very least strongly influenced by jazz.
But really, when most listeners think of jazz-pop, they think of it in the post-rock & roll era. During the '60s, two dominant strains of jazz-pop developed. The first was a mellow, smooth, almost easy-listening strain of jazzy pop epitomized by artists like the Dixieland-influenced Al Hirt and the Latin-tinged Herb Alpert. The other sprang up as a sort of middle ground between the grooving, funky soul-jazz that became popular during the decade, and instrumental soul artists like Junior Walker and the Stax/Volt combos (Booker T. & the MG's, the Mar-Keys, the Bar-Kays). In this vein, the Ramsey Lewis Trio scored a pop smash in 1965 with their catchy "The In Crowd," and the trio's rhythm section -- reconstituted as Young-Holt Unlimited -- repeated the feat in 1969 with "Soulful Strut."
As fusion introduced rock and funk rhythms into the vocabularies of more and more jazz artists, jazz-pop began to mirror the shifting musical landscape, in the process reaching a wider audience than ever before. Artists like Chuck Mangione, Spyro Gyra, Bob James, and George Benson became stars in the mid- to late '70s, with the balance between pop, jazz, and R&B influences varying according to the individual. Purists and many critics decried the slick polish and simplicity of the new breed of jazz-pop, plus what they viewed as commercial pandering and blandly pleasant predictability; during the '80s, their concerns came to be symbolized by the wildly popular soprano saxophonist Kenny G, who sold millions of albums and proved that instrumental jazz-pop could cross over to pop and adult contemporary audiences. During the '90s, Kenny G's success helped give rise to the smooth jazz radio format, which steered jazz-pop in a similarly polished, pleasantly soothing direction.