The Warner Theatre is still standing. Proving, perhaps once and for all, the basic sturdiness of an earlier, grander era of American architecture, the old building last night withstood the music of Blackfoot and Def Leopard.

Backed (or, rather, almost surrounded) by a wall of speakers which took up half the stage, the musicians flailed away at their guitars and drums in a show which tested the limits of musical, as well as structural, integrity.

Def Leopard opened with a set most notable for its paucity of redeeming musical quality. Melody, harmony, rhythmic and dynamic nuance were simply not a part of the group's musical sensibility. Quasi-blues solos, an imitation Mick Jagger stage act and plodding beats were, however, and each was delivered with mindless abandon.

Blackfoot, on the other hand, did include melody, harmony, rhythmic and dynamic nuance, all buried under the aforementioned shoelace-shaking decibel level. What one could hear (whether one wanted to or not) were the screeching guitars, thumping bass and the 2 1/2 words which apparently comprised the lead singer's vocabulary -- "rock 'n' roll!" -- which he uttered incessantly.

Def Leopard and Blackfoot are heavy metal at its best, which is to say, rock music at its worst.