Jazz, which is to say "revolting rubbish" and "ideological poison" in the words of old-line Stalinist critics, proved to be red-hot as Russians of all ages packed an auditorium of the Soviet Composers Union to hear a seven-man New Orleans band.

An equally large crowd waited outside in hopes of catching a glimpse of the Louisiana Repertory Jazz Ensemble, which performed here despite the absence of a Soviet-American cultural exchange agreement, and the chill on U.S.-Soviet relations.

The jam session Wednesday night with a score of top Soviet jazz musicians was the high point of the concert for the band that holds forth regularly on Wednesday nights at the Maple Leaf Bar in New Orleans.

The leader of the Americans, Frederick Starr, is largely responsible for an unusually warm interchange. Speaking fluent Russian, Starr managed to break the traditional reserve of the Soviet audience.

He would like, he told the audience, to invite a Soviet jazz group to visit the United States.

"Since we don't have a union of composers, I can invite them only to the Maple Leaf Bar. The place is sort of grubby and certainly not as elegant as this, but there are free drinks on the house."

The crowd roared.

The Soviet Composers Union is the bastion of traditionalism. It is still run by Tikhon Khrennikov, the man whom Stalin appointed as music overlord in 1948.

During the first decade of Khrennikov's tenure, jazz was vilified as "rubbish," or, in the words of Maxim Gorki, as "musica tolstih" (the music of the fat people).

Nowadays, however, jazz has been admitted to respectability, and Starr could poke fun and elicit laughter from the audience by pointing to his banjo player, John Chaffee, who weighs about 200 pounds, as proof that Gorki's assessment was right.

The band was invited to visit here by the American ambassador, Arthur Hartman, who has been trying some unorthodox approaches to increase the U.S. presence in the Soviet Union despite the coolness of bilateral relations.

The trip was largely financed by donations, including a major grant by Pepsico Chairman Donald M. Kendall.

Hartman's choice of Starr seemed particularly fortuitous.

Starr, 43, a historian by profession, spent two years at Leningrad University. He subsequently taught history at Princeton, served as secretary of the Kennan Institute for Advanced Russian Studies at the Woodrow Wilson International Center for Scholars in Washington, and was vice chancellor of Tulane University in New Orleans before recently being named president of Oberlin College in Ohio.

While he lived in Washington, Starr played with a band called the Federal Jazz Commission. When he moved to New Orleans three years ago, he organized the Louisiana Repertory Jazz Ensemble. It has built a reputation for successfully resuscitating jazz of the 1890-1930 era, heard otherwise mostly on old records of poor technical quality.

Starr combined his interest in Russian history and his love of jazz to research and write a history of jazz in the Soviet Union. The book, "Red and Hot" is due to be published in April by Oxford University Press.

As a result, the band not only attracted the luminaries of Soviet cultural life but virtually all important jazz musicians and critics. Walter Ojakaar of Tallinn, the Leningrad critic Vladimir Feyertag and prominent Moscow jazz experts, including Leonid Pereverzov, were in the audience.

Joining the Americans to play on stage were pianist Igor Brill, horn player Gherman Lukianov, saxaphonist Alexei Kozlov, pianist Leonid Chizhik, trombone player Vladimir Lebedev and clarinetist Lev Lebedev. Laszlo Olkah, now in his seventies, demonstrated his skills as a drummer.

The arrival of the U.S. band was not advertised, yet word of its appearance at the Composers Union hall spread quickly.

If there were one thing noticeable as the Americans and Russians kept changing on the stage until past midnight, it was the highly individualistic style of Soviet performers contrasted with the tightly integrated collective style of the Americans.

The American players later commented that most of the Russian players were up to world standards and would astonish and impress people in American city.

For the seven-man band, with the exception of Starr, this was the first visit to the Soviet Union. Ranging in age from 27 to 71, they found the trip worthwhile.

As trombonist Fred Lonzo put it, "Man, it is interesting. We arrived on New Year's Eve and we are leaving on Christmas Eve. That can only happen in Russia."

Thursday night was Christmas Eve in the Russian tradition, and the band left by train for Leningrad, where it will give two concerts before returning home.