``Hydrogen Jukebox,'' 21 poems by ``beat'' poet Allen Ginsberg set to music by Philip Glass, was splendidly sung but difficult to understand in its staged premiere at the Spoleto Festival. It's presented as an ``acted'' song cycle, with much arm moving, walking and rolling around the stage by six splendid singers. Few words are understandable, far fewer than in most new operas in English. In an opera, when words aren't understood, the audience can get the gist of what's going on from the plot. But in Ginsberg's poems of free association, symbolism, fanciful happenings, inside allusions and non sequiturs abound, and one line of poetry often has no relation to the line before. The work desperately needs surtitles. We saw Monday night's performance, the third, in the Sottile Theater. We were able to realize there are anti-war poems, many references to India, nature, politics and industry, with appropriate back-wall projections. Glass' music was usually a melody, which the singers _ James Butler, Richard Fracker, Suzan Hanson, Thomas N. Potter, Linda Thompson and Darynn Zimmer _ sang over repetitive figures instead of chords. Each singer has a fine, distinctive voice, and they blended beautifully. Following the Spoleto Festival U.S.A., ``Hydrogen Jukebox'' will be performed at the Festival of Two Worlds in Spoleto, Italy June 27 through July 15. A year from this fall, there are plans to tour ``Hydrogen Jukebox'' to 40 or 50 American cities. In great contrast was Mozart's ``The Marriage of Figaro'' from 1786, in the Dock Street Theater. Gian Carlo Menotti, artistic director of Spoleto Festival U.S.A., staged it. It became the hit of last year's festival and was repeated eight times this year, quickly selling out. The production is warm and friendly. Spiros Argiris conducted so briskly that some singers, especially Hilda Harris as Cherubino, had difficulty. Renee Fleming from Indiana, Pa., is probably the best Countess we've ever heard. Also fine were Erich Parce, Figaro; Young Ok Shin, Susanna, and Christopher Trakas, the Count. Menotti's grandson, Claudio, nearly 3, made his stage debut Saturday night as the son of the Count and Countess, with notable stage presence. Our biggest surprise at the festival was the sold-out ``Birth of an American Avant Garde'' concert at the College of Charleston. Host, composer John Kennedy, said that no piece on the program had been played more than a handful of times. The hit was William Russell's ``Four Dance Movements,'' three written in 1933 and one in 1990, and his 1936 ``Made in America,'' first performed in 1990. The concert, which included playing a suitcase, was at its most fun when Kennedy donned goggles and one glove and hammered a bottle to bits over a metal garbage can. Peter Garland was inspired by Indians and Johanna M. Beyer by a one-string instrument called a lion's roar, both at too much length. A 1971 James Tenney early minimalist piece completed the program. Old festival hands were saying there was the most experimentation ever this year. A sold-out chamber music concert at the Dock Street Theater, hosted in laid-back, knowledgeable, amusing style by Charles Wadsworth, sandwiched the premiere of Frazelle's ``String Trio'' between Bach and Vivaldi. The Memorial Day weekend streets of Charleston were crowded with people walking among 11 theaters, some going to concerts morning, afternoon and evening. Menotti said Tuesday that his greatest joy is introducing the arts to people who've never experienced them before.