Jazz and popular music have been having an on-again, off-again affair for years. At times, jazz becomes too introspective and inaccessible for popular tastes, while pop becomes a trifle too accessible for jazz ears. At the moment, however, they are getting along just fine.

The Tom Browne Sextet, which appeared last night (and will appear tonight) at the Cellar Door, is one of the new additions to the Pop-Jazz Scene. Like their counterparts (George Benson is the best example) the group features warm harmonies and smooth, if somewhat predictable, playing which is aimed more at the feet than at the mind. The wistful melodies and jumpy rhythms demand nothing of the listeners except a willingness to be entertained.

Leader Tom Browne is a skilled musician, but his trumpet and fluegelhorn work is heardly inspiring. His solos, and those of his fellow musicians, were finely constructed and perfectly suited to the easygoing music, yet they lacked any feeling or fire.

But of course feeling and fire have never been a part of pop jazz and probably never will be.The style does not deal in artistic confrontation so much as relaxed musical enjoyment. The Tom Browne Sextet certainly doesn't take any chances, but they are pleasant and hummable and . . . entertaining.