The "Sonancias" of Marlos Nobre might have been composed for performance in the Hall of the Americas at the Organization of American States--an enormous, high-ceilinged room full of quirky echoes, where a solo flute can sometimes sound like a flute duet and the low, gentle voice of a viola can disappear almost completely.

The "Sonancias" are an intense encounter between piano and percussion--sometimes a dialogue, occasionally a duel and at climactic points a sort of reconciliation. The Brazilian composer calls for great, crashing bass chords from the piano, held interminably--shimmering and slowly dying in the hall's acoustics. Last night in the Inter-American Music Festival, the piano chords often hung in the air like a thundercloud with other sounds (cymbals, tympani, wood blocks or the piano's treble keys) flashed through it like bolts of lightning. The effect was magnificent--overwhelming.

The OAS ambiance was also good for the "Ocho Por Radio" of Silvestre Revueltas, which is essentially outdoor music although it was composed (as the title indicates) for radio performance. The eight instruments sound like a dissonant mariachi band (without guitar but with a tambourine), the kind of music Charles Ives might have composed if he had been born in Mexico.

The third charmer on the program, "Darkness Songs" by Stephen Block, was not helped by the hall's acoustics. It includes five American Indian poems read by a narrator, with a musical background and commentary by six instrumentalists, and it had many compelling moments despite a synergy between room acoustics and a sound system that made many of the spoken lines unintelligible.

"Black Mamba" by Andrew Thomas is a colorful, fast-moving, sometimes noisy piece, well-constructed with a fine sense of climax and piquant Afro-American flavors in the rhythms--a touch of North American jazz and a graceful borrowing of Brazilian dance rhythms. Two other pieces seemed well-made but less charming. They were the intricately dry "Winter Counterpoint" of Max Lifchitz (a Mexican composer despite the non-Spanish name) and the terse, epigrammatic "Serenade for Five Instruments" by David Stock, conductor of the chamber ensemble. While it was hardly a complete survey of what is happening in chamber music, the program gave an impressive and highly enjoyable survey of some high points.