The job of a studio musician or singer is to create a pleasing, supportive background. The six members of L.A.'s Toto were pros at this before forming their own group. Realizing that many listeners used the radio and records as background, they adopted a quite bankable strategy: They made their own records without the distraction of a strong personality in the foreground.

They succeed only too well on "Toto IV," which is flawless as well as faceless. And heartless: the melodies never original but always catchy, the singing insipid but soothing, the playing soulless but skilled -- and boasting the best in modern technology. Toto has updated Chicago's popular blandness with the electric keyboards of David Paich and Steve Porcaro and the synthesized guitar of Steve Lukather, especially on the Chicago-plus-Boston-like "Good For You." "Rosanna," the album's hit single, features a melody as jingly as any commercial and a wash of synthesizers as inoffensive as a space opera soundtrack.

Much of the album sounds as if it had been created by a computer analysis of the last six months' record charts: pleasant and perfect. So-called experimentalists like Kraftwerk, who seek to minimize the human presence in music, should take lessons from Toto. ON RECORD, ON STAGE THE ALBUM: "Toto IV"(Columbia SC 37728). THE CONCERT: Toto with Frankie & The Knockouts at the Merriweather Post Pavilion, Sunday at 7:30.