"Chorus" is a Greek word, hardly changed from its original form, as are such other splendid concepts as "democracy," "philosophy" and, come to think of it, "music." For our culture, the Greeks invented choral singing--as an art form, rather than a random happening. That fine old tradition is still in good hands, according to the evidence presented last night in the Lisner Auditorium by the Experimental Choir of Athens, an a cappella male chorus of about 30 voices with a very high level of polish and discipline.

The program included a few brief works by such Western composers as Palestrina and Josquin DesPrez, but its focus was a survey of Greek music, from ancient Byzantine chants to folk songs and the work of such modern composers as Theodorakis--arranged by the choir's director, Dimitris Papapostolou, and performed with very refined dynamic nuances and splendid balance. There was a stunning tonal beauty from deep bass to the counter-tenor range, and the conductor's control of the material seemed absolute--not only in the performance, but in the harmonic fabric of the music itself.

The objective, a program note explained, was "to present Greek music through the ages as viewed by contemporary man," converting the intricate monophonic melodies to "a new harmonic form while keeping the character of the song intact." That is a fair description of what could be heard last night. Along with the advantages of a very high level of refinement, the music had some disadvantages inherent in the professed effort to make "Greek music palatable to more than the Greek ear."

The Greek word "choros" originally meant a group that dances as it sings, and the pulse of dance rhythms has always been one of the strengths of Greek music. Others are a special spice in the non-triadic harmonies, and bends in the solo vocal lines that find compelling musical substance where other idioms seem tone deaf--for example, in the space between F and F-sharp. In the first half of the program, where the material was translated into contemporary international choral idioms, much of this special flavor was lost, or reduced to the merest hint. It came back strongly, however, in the second half, when the chorus was joined by soloists and a wealth of folk material was presented with relatively little rearrangement.

Between these choral segments, a series of solo songs (chiefly by Theodorakis and Hadjidakis) was presented by mezzo-soprano Joan Sfekas-Karvelas of Baltimore, a voice well-trained for Western art song, rich in tone, attuned to this music's special qualities and beautifully accompanied by pianist Neil Ratliff. Once again, as it approached the style of our standard concert repertoire, the uniquely Greek flavor of the music was somewhat attenuated. But its quality was clearly presented and it was highly enjoyable.