Rock 'n' roll has undergone major surgery during the past 20 years, and the changes have not always been for the better. After listening to the rough-hewn "Pretenders" album and Todd Rundgren's polished "Adventures in Utopia," an apprehension sneaks out of the comparison, an ambivalence about the value of Hi-Tech in an industry born of vulgarity.

"Pretenders" is square, honest, brazenly upfront in its rock 'n' roll; it is also precocious and crudely produced. Rundgren's release has none of this raw audacity, but it is slick and marketable.

What is remarkable about the Pretenders is what is remarkable about most New Rock. There's a compassionate respect for raw materials: two or three guitars, a set of drums, maybe a keyboard and harmonica and a caustic vocal. Rock was born and flourished on these materials -- before the engineers, producers, packaging design firms, movies, TV and promo-conmen got hold of it -- when raw instruments were the end of the music, not a means to it.

The Pretenders use both the raw and the processed rock 'n' roll. Three haphazard guitars hammer at an unimaginative but terribly regular drummer. The raunchy, amorphous rhythmchording sounds almost like a high school rock band in a resonating gymnasium. Arrangements are either parodies of early nocturnal rock, or potpourri of old rock and new wave motifs, accompanied by the crude, rasping vocals and vulgar lyrics of Chrissie Hynde. Like the seedy band behind her, Hynde is crude and also familiar, a hybrid of Patti Smith, Grace Slick and Cher.

All this raw raunchiness, when thrown together, smacks of real rock 'n' roll. There's an anxious naivete in the Pretenders. It's almost as if they don't quite know what to do with all the vulgarity. Perhaps it's this naive depravity that inspired a New York rock aficionado to deify the Pretenders as "the saviors of rock 'n' roll." If the Pretenders are saviors, it's because they make no bones about where rock came from.

After "Sgt. Pepper," however, the roles of music and instrumentation were perversely reversed; instrumentation became a means to an often ornamental sound. Rock became slick.

So slick, so calculatedly clean is the new Todd Rundgren album that it comes across like a capsule of every Top-Pop 40 group since Yes. It's rock 'n' roll as Formula, rock as Product, rock as Industry. Nothing of the perfect is missing here: the cute, bouncy, catchy tunes; the heavy syncopated bass and drum lines; the airy harmonies so assiduously punctuated by vocal exclamations and guitar riffs; a Studio Sound, so neatly pruned, packaged and produced. We marvel more at the recording technology than at the music.

Perhaps all this slickness can be explained away and Todd Rundgren excused. The songs were "originally performed for the Utopia video television production UTOPIA." Blame the vapid formula, the insipid lyrics ("Everyday it's the same old situation/I race the same old line of empty faces") on TV, the "cool" slick medium. But "Adventures in Utopia" has been released as rock 'n' roll. What happened to rock 'n' roll? What happened to the raw materials.