The attire of the rock group Chicago, appearing at the Merriweather Post Pavilion through tonight, ranges from jogging suits to skin-tight leather to Las Vegas Sleaze. And the quality of the music also runs a wide spectrum - from the tasteful to the abhorent.

Frist the tasteful: Pop tunes like "Saturday in the Park," "If You Leave Me Now," and "Take Me Back to Chicago," well-written and cleverly arranged, allow Chicago's horn section to subtly embellish the stylish vocals.

But how abhorrent the rest of the evening! With disturbing regularity Chicago shed its tasteful pop for hard rock of the crudest sort. Wave upon wave of relentless sound, insulting the senses, became its mark, each note barely distinguishable from the next. In sum, loud but boring.

Unlike superior acts, Chicago scores only with stellar material; it is unable to make a mediocre song shine. A good tune - and Chicago is a success. A passable tune - and Chicago simply makes noise.

But not to the high schoolers at the Post Pavilion last night. At the concert's end, as at a football game, they chanted "We won't go." They got their encore the rock standard "I'm a Man," a good tune - and well done.