Even with the 45 performers carefully rehearsed and projecting near-professionally, a Zivio concert retains its spontaneous charm. You have a feeling of looking in on an impromptu folk gathering, where the dancers and singers really enjoy themselves. And the disciplined singers perform everything from memory in these difficult Slavic languages.

Dancers of Zivio first transported their audience to Croatia, for a well-integrated group of songs and dances that incorporated the drmes, in the jumping, shaking Lakocsa of the men, with its boot-slapping rhythms.Perhaps most memorable was the choral music of Croatia with its plaintive, rhythmic airs, followed by a suite choreographed by Zeliko Jergan, from Posavina - an area along the River Sava. The river societies of the Slavic lands carry into their music and dances a certain flowing, undulating charm that suggests the psychological influence of the rivers, with their alternate slow, lazy currents and rushing waters. The rivers seem to have formed the people's lifestyle and nature in a way.

Twenty or more dancers in white with red trimming - women in long skirts, men in tunics and trousers, all in slippers with turned-up toes, danced these lively, amiable dances, characterized by jumping, accelerating rhythms. The Ducec, or hopping dance, showed where the Bunny Hop came from with its energetic excesses, followed by the lively Posavski Drmes, a bouncy, saucy dance.

The interestingly arranged program frequently alternated singing by groups that combined and recombined, yet maintained their blend and brought out the nasal, white tones of these peoples with their expressive phrases and sonorous chordal progressions. It's no easy task to sound as authentic as these singers and instrumentalists do, sustained by Brian Salisbury's dependable violin and another dozen players on the conventional accordion, flute, guitar and clarinet, plus the more exotic gudulka, mandolin and of course the haunting tamburitzas. And as always it was a luxury to enjoy such authentic music with the dances.

Artistic director Barry Goldman choreographed Dances of Szekely (Hungary) in Transylvania - lively, swinging dances for couples, with much stamping among their repetitive steps.

You may not stay up with every dance and its characteristics as they are performed, but you will enjoy the kaleidoscope of forms and variations that swirls past you in a Zivio concert. Line dances, circle dances, couple dances and squares show where many of our Americandances come from.

A Bulgarian Suite with its long line of brightly costumed dancers, and songs of Bulgaria comprised the second half of the concert, along with songs and dances of the United States, reels and squares that have mostly been seen on previous programs.

- TWO CALIFORNIA THEATERS, probably motivated by fear of boycott, refused to allow AVAZ International Dance Theatre to perform Middle Eastern dances in their facilities for the 1991-92 season. When the company refused to alter their program, their performances were canceled.

The 55-member company specializes in dances and music of Eastern Europe, the Caucasus, Central Asia, North Africa and the Middle East.

Though understanding that Middle Eastern dance may not be at the height of its popularity, artistic director Anthony Shay feels that Americans need understanding of the peoples in that part of the world, which dance and the other arts can give.