The Los Angeles Philharmonic Institute Orchestra is of necessity a protean thing. Personnel changes from season to season are probably close to total, and the orchestra is led and rehearsed each summer by a varied cast of conductors.
Sunday at Hollywood Bowl, the playing of the sixth Institute Orchestra steadily improved throughout the evening. That may reflect growing confidence, adaptation to Bowl acoustics or attitudes toward different leaders, as well as the technical challenge of the music at hand.
Lukas Foss, one of the institute's two directors for 1987, gave the young musicians thorough exposure to the currently popular cheerleading style of conducting. Working without score or baton, he stomped, hopped and waved, strutted like a berserk marionette and shook his fists dramatically in behalf of Tchaikovsky's "Pathetique" Symphony.
His charges loved it, to judge from their demonstration at the end. The musical evidence, however, was less conclusive. The always ardent playing made striking gains in balance and intonation over earlier efforts, but cohesion and clarity were still lacking.