SALZBURG, Austria (AP) _ American artists are playing a prominent part at this year's Salzburg Festival, as one of the world's most prestigious but tradition-bound cultural institutions searches for a new repertoire and a new place in the hearts of the public.

American performers, particularly jazz legends who have few equals in Europe, have long made the trans-Atlantic trek to summer festivals or on grueling tours intended to enhance both reputation and bank balance.

But Salzburg, imperiously dominated for decades by its modern-day favorite son, the legendary conductor Herbert von Karajan, was off-limits to all but a American few stars like Jessye Norman - a no-show this year due to illness - and carefully selected orchestras.

It has taken three years since von Karajan died in 1989 to begin the vast and controversial task of revamping the festival by introducing new artists, orchestras and modern music and drama to conservative audiences paying up to $360 each for opera or top concerts.

''If von Karajan were still alive, we wouldn't be here today,'' said Byron Peebles, 61, a trombonist with the Los Angeles Philarmonic, which made its Salzburg debut under 34-year-old Finnish conductor Esa-Pekka Salonen.

This year's concert season opened with three performances by the Cleveland Orchestra. On their heels came the Los Angeles musicians, the first American orchestra invited to Mozart's birthplace to perform both concerts and opera.

Add to that Salzburg's new darling, soprano Cheryl Struder, director Peter Sellars, composer-in-residence George Crumb and a host of lesser names, and you have a festival rolling in Americans often more valued in Europe than at home.

In the fringe festival, Salzburg ''Scene,'' Texas-born Robert Wilson, billed as the world's most sought-after avant-garde director, took a starring role with his production of a 1938 work by Gertrude Stein.

For those who wanted simply to hang loose, folk star Tracy Chapman sent her dulcet pleas for ''Revolution'' and social change reverberating through Salzburg with an open-air concert on the Cathedral Square.

The change of festival repertoire and emphasis on what some saw as an untried orchestra from Hollywood are not popular with everybody, particularly the exacting, conservative and often partisan Austrian critics.

''Turnips and cabbages - albeit with high value in vitamins,'' wrote the local Salzburger Nachrichten daily of Cleveland's first concert.

The Los Angeles orchestra fared even worse after its first concert, dubbed ''a provocation in the mouth of the lion'' by the Salzburg newspaper for its all-Viennese program of Johann Strauss' Emperor's Waltz, Alban Berg's violin concerto and Gustav Mahler's fourth symphony.

''Canned music from U.S. drugstores,'' said the Neue Kronen Zeitung.

The criticism reflected the conviction of some Austrian critics that Viennese music (and the Salzburg Festival) are the preserve of the Vienna Philarmonic, and that American ensembles - however technically perfect - cannot compete.

Still, the Americans brought a zest to Salzburg missing in Viennese musicians who regard playing here as a virtual birthright.

''It's just very exciting to be in a position to know that we can participate at this level,'' enthused Roy Tanabe, 54, violinist and assistant personnel manager with the Los Angeles orchestra.

Sellars and others invited to this cultural extravaganza - budgeted at $42 million for a six-week orgy of fine opera, concerts and drama - have the satisfaction of working with the finest.

''I could never put this show up in the United States,'' noted Sellars as he marveled at the complex authenticity of the mock cathedral European craftsmen built for just four performances of the Messiaen.

Other aspects of European technology drew less praise. The Los Angeles orchestra refused one Sunday to play in its appointed rehearsal hall, a broiling wood and glass construction lacking air conditioning in rare 90- degree heat. The next rehearsals took place in the ill-lit, but air- conditioned ballroom of a local hotel.