"Ladies and gentlemen. A legend in their own time -- Chicago!" With that introduction behind them, the nine members of Chicago walked out on stage at Merriweather Post Pavilion Saturday night and attempted to live up to their self-appointed status. It wasn't always easy.

For one thing, the group had to contend with an unbalanced sound mix early in the show. The first few songs were obliterated by a blast of percussion that muted the horn section and made Pete Cetera's singing all but inaudible.

Then there was the problem of material. Over the course of a dozen years and 14 albums, Chicago has accumulated more songs than even they care to remember. Unfortunately, though, most of their arrangements rely on similar patterns -- polyrhythmic percussion, rising brass figures and pinched guitar fills. Now that the vocals are split exclusively between Cetera and Robert Lamm, an undeniable sameness prevents them from building much momentum.

Nonetheless, Chicago managed to make the most of songs like "No Tell Lovers," "Feelin' Stronger" and "If You Leave Me Now," to compensate for the lapses in between them, and trombonist James Pankow assisted Lamm and Cetera in bringing a personal touch to the music.

And for their diehard fans -- who else would recognize "Saturday in the Park," upon hearing only the first chord? -- the entire concert was indeed the stuff of which legends are made. They're probably making plans right about now to see Chicago again next year.