Last night at the Kennedy Center, Riccardo Muti and the Philadelphia Orchestra opened their first concert of the season here with "Lontano" by Gyo rgy Ligeti -- a bold gesture for any orchestra and downright reckless, one might think, for the conservative Philadelphia.

Ligeti has been a leader of the avant-garde since the '60s, and "Lontano" ("Distant"), which is now 20 years old, shows how he reached that status. For long stretches, this radiant but slow-moving music seems simply to hang in the air, glowing and gradually developing. But this is not minimal music; there is forward motion and form in its constantly shifting perspectives.

It is evocative music, though not as overtly or with as much definition as Beethoven's "Pastoral" Symphony, which finished the evening in a precise, mellow, beautifully paced and phrased performance. Beginning the program with Ligeti's kind of evocation and ending it with Beethoven's constituted a musical statement of considerable coherence and interest. Still, an opinion that must be widely held was vividly expressed by one musically sensitive if not adventurous member of the audience as the applause for the Ligeti was fading away: "Now that they've finished tuning up, maybe we'll hear some music."

Between these two dialectical opposites, the slender, melodious, post-Mozartian Piano Concerto No. 1 of Carl Maria von Weber received a fluent, poetic, technically assured performance with Malcolm Frager as soloist. Making its Kennedy Center debut under Frager's fingers was a new American piano he is trying out -- the Falcone.

On first hearing, it seemed a pleasant instrument with a particularly sweet and clear upper register, homogeneous voicing and good dynamic balance across the keyboard. One would like to hear this piano in Tchaikovsky or Prokofiev before making a final judgment, but what it did last night was well done.