"Is this an intermission or was that the end?" a puzzled patron asked an usher last night in the Kennedy Center Concert Hall. It was almost 10 p.m. and the first break had come in a concert that began almost exactly at 8:30. "I don't know," said the usher. "Nobody knows, but we're going to check." He dashed to a house phone and came back with a one-word message: "Intermission."

The incident typified a concert rich in its musical content but poorly prepared and badly presented. When Mikis Theodorakis came on stage for his concert last night, nobody in the Kennedy Center knew exactly what music he would perform except perhaps the musicians. The presentation seemed haphazard, with no particular logic evident in the music's selection or order. And the intermission seemed to come not at a carefully calculated point but when Theodorakis decided it was time for a break.

Outside of the music (which communicates eloquently), there was no communication with the audience. None of the music (or the performers) was introduced from the stage, and the program simply announced "classical works and popular songs sung throughout Greece" with no specifics. This is not very helpful, since Theodorakis is one of the most prolific as well as one of the most distinctive living composers.

The opus numbers of his classical works passed the 100 mark in 1969, and this category does not include hundreds of popular songs that may be chart-busters in Greece but are unfamiliar to most Americans. The soundtrack composer for "Zorba the Greek," "Z," "State of Siege" and "Serpico" should not have to limit himself to an ethnic audience in the United States. But that is essentially what he did. He was performing in America but not for Americans. He could learn a lesson from other foreign performers, such as the Frenchman Charles Aznavour. Or from a Ukrainian concert that was given for a Ukrainian audience in the same auditorium last month, with each selection carefully listed and annotated in English.

His music has a universal appeal if people are given half a chance to like it. It has smashed through the barriers that usually put folk, popular and classical music in airtight compartments, thereby enriching all three categories. It is brilliantly colored music, deeply emotional and highly kinetic, music that makes it almost impossible not to get up and dance. But most people need help in approaching it, and last night none was offered. Theodorakis was preaching to those who already believe, and the Concert Hall was only one-third full.

The performance was not equal to what one hears on his records, or to the memories of his last appearance here in the '70s. Maria Farandouri, the handpicked interpeter of his deepest and most durable works, was a serious disappointment. Her voice still has its familiar expressiveness and emotional urgency, but her tone is the merest shadow of its former glory. Petros Pandis talked his way eloquently through a number of songs, but he is billed as a singer. Perhaps to spare these voices, most of the evening's singing assignments were given to Thanasis Moraitis, a pop singer of high energy and good technique, if not much depth.

The virtuoso bouzouki playing of Andreas Michalakis was one of the evening's highlights, and the whole eight-piece ensemble called the Socrates Orchestra was excellent. But in spite of some impressive performances, the concert did not really give the music the chance it deserves.