"The first day we were afraid. The aggressiveness in the air, you could almost feel it." With the help of an interpreter. Hungarian-born composer-musician Yochk'o Seffer was attempting to describe his first impressions of New York City and the United States.

He spoke softly, deliberately. He slipped from the couch, onto the floor, leaned against a coffee table, his eyebrows raised. "But you know, this country is so big, so formidable. There are so many different people and things that are all together. The Europeans are compartmentalized - Belgians, French, Germans, da, da, da. If I want to call a friend, 300 miles away, I must call another country. It's stupid."

Maybe it's the enthusiasm in his voice, or the flash of intense emotion that breaks across his placid face at times. Somewhere, beneath the well-groomed.Continental exterior, the fiery spirit of the gypsy smolders within Yochk'o Seffer.

That spirit, which has taken him from Hungary to Finland and France, where he has lived since 1957, has now brought him to the United States in search of new listeners for his music - music being offered by some of its adherents as an alternative to contemporary rock. His American debut was at Blues Alley, last week, after which he played the Rogue and Jar and the One Step Down before heading north to the Zu Manifestival of alternative music in New York.

Seffer came to make his impression on the big, formidable United States, which so far hardly knows he exists. He has gained some attention in Europe, where he's played various music festivals, and French television is planning a one-hour special on him soon; but although some of his records are available in Washington stores, the market for imported jazz is limited. "His music is very specialized," says Myron Bretholz of Record and Tape Ltd, "which means that it isn't very commercial."

The Washington engagements came about when Jamil Guellal, a disc jockey at WGTB-FM, went to Paris this summer to interview French musicians for his program, "Mixage." Seffer said he wanted to play the U.S.A., and Guellal agreed to talk to some club owners. Nobody, including Seffer, expects this visit to the lucrative. But it may break down some of the barriers that Seffer is concerned about - barriers that separate people, and that separate different styles of music.

"I hate labels - rock, classical, jazz. Most people need them, but they are bad for music." Seffer's eyes flicker for a moment.

"European music teachers hate jazz. It's the old battle between 'serious' and 'club' musicians. To be considered serious to them you must be a classical musician. It's not true."

Barriers have been the landmarks in Seffer's life and musical career. He left Hungary in 1956 at the height of the uprising. He is reticent about discussing the subject. "I am apolitical," he says, shaking his head defiantly. "I am a traveler. We were nine musicians who decided to go, that's all."

Yet the feelings persist.While listening to a French recording of "Marocksek," his composition about the crossing of the Hungarian frontier, Sheffer, 39, recalls the scene that inspired the music. "The village was being bombed. Everyone was in a panic. I was asthmatic. It was very difficult."

As the eerie sound of sirens, wails and bombs echoed within the stark, abstract music, Seffer became quiet, thoughtful. He was 17 at the time.

The mood passed quickly as Seffer talked about his work, for he has crossed as much musical as geographical terrain. His father and grandfather played with the opera in his native Miskolc and he studied the clarinet as a child. In a picture of his early school orchestra, he is seen sitting demurely behind an old music stand like those used by the big bands.

"My old band," he says, beaming. "We played Benny Goodman." The blurry picture evoked an earlier, more naive time, when the strains of Hungarian big-band jazz drifted across the Russian border.

During these years, he became fascinated by Hungarian folk music and the work of composer Bela Bartok. "I feel like this music belongs to me," he says emphatically. And the energy, the "feel" of the folk rhythms, brought him to American jazz. "With classical music, you have the mind. It is intellectual, where jazz comes from the stomach."

His discovery of the music of saxophonist John Coltrane had an energizing effect. "Coltrane is a beast. I mean that in a good sense. He is the great one." Seffer was excited. His manager, George Leton, pulled several records from a case and produced one by Perception, a group which Seffer formed in 1969. The record sounds similar to Coltrane's trailblazing work of the mid-60s. Dense textures of improvised sound. Wild, savage, yet somehow controlled.

"My music is much different now. I can never stand still." As Leton played each record, the questing nature of Seffer's music became more apparent. The strict jazz approach was abandoned with Magma, a group which recorded eight records from 1970 to 1973.

Rock beats were added and a new "language" was devised for the vocalist. "The words have no meaning. They are basically syllables that were designed to accent the musical sounds." The "words" spilled from the speakers in sharp, staccato phrases. Seffer sank back into the couch, eyes closed, foot tapping, savering the foreign-sounding voice.

While listening to another record, he sat up suddenly: "Listen. This is an instrument I have invented. It's called a Malaber, named for the popular French lollypop." The device, which is made out of a vacuum cleaner hose and a plastic bottle, emits a nasal, high-pitched sound like that of a Middle Eastern instrument, and is capable of producing three tones simultaneously. Seffer plays nine conventional instruments (including saxes, flutes and piano), and the seven more he has invented add an alien presence to his music.

New languages. New instruments. Seffer delights in working with sound and devising new means of supplementing conventional musical ideas. While talking about his career of personal background, he is reserved, polite. But when he discusses his ideas he gestures with his hands, the eyes light up, and he appears consumed by irresistible nervous energy.

Memories of his classical study as a child and later at the Paris Conservatory spill out: "The professors are mostly bureaucrats. They teach you the theories and procedures but they know nothing about the emotions." Anger colors his face momentarily. "They can't see that substance is more important than stylistic differences."

He studied with Nadia Boulanger at Fountainbleau, where his fellow students included Lalo Schifrin and Donald Bird.

"She was much different. She has her own ideas and is very sure of them. But she allows you to develop your own abilities."

Seffer's musical evolution went full tilt when, after classical, jazz, then rock playing, he added a string quartet to his group, Zao, in the mid-'70s. His compositions became strictly notated, with sections reserved for solo improvisation and rock beats that were spiced with the rhythmic inflections of Bartok and Stravinsky. The result was a synthesis of the three styles that blurred the distinctions between them.

"I added the four females," he said, poking himself in the face and drawing laughter. "My wife would kill me. You see, in France, we only use the word 'females' for animals." Serious again. "The quartet added a new dimension to the music."

That new dimension was a classical discipline that, when added to the energy of the rock and the emotion of the jazz, produced an intriguing new style of music that Seffer calls "spiritual." In 1976, he left Zao and formed Neffesh-Music, his present ensemble, which will be represented in the United States by himself, drummer Francois Laizeau, American bass player David Kassler, and the "four females" on pre-recorded tape.

"We could not afford to bring the entire group and we decided to use the tape, which should work well because the compositions are written out." Although playing with a tape in concert is difficult, he believes it is the only way his music could be adequately presented.

This music is the result of his study of the Kabala philosophy, which dates from the 13th century. At that time, Spaniards were attempting a synthesis of the world's major philosophies and theologies. "They wanted to unify the beliefs, not separate them. And that is what I am trying to do, musically."

Has he succeeded?

Seffer only smiled - at the moment his prospects were bright: meeting new musicians, hearing new sounds and seeing a new country.