Glamor in the hall vied with brilliance on stage at the Kennedy Center Saturday night as a predominantly black-tie audience of diplomatic, government and business representatives gathered for a concert by the Mexico Philharmonic Orchestra.

Under director Fernando Lozano the Philharmonic played with a bright, extroverted style that worked especially well in the opening Second Symphony of the Mexican composer Carlos Chavez. The piece, which uses authentic Indian melodies, requires rhythmic verve and a big sound, which the orchestra supplied in abundance. Jorge Federico Osorio made a strong soloist in Prokofiev's First Piano Concerto, attacking its fiendish piano part with an exciting power and vigor, though realizing little of the contrasting lyrical passages.

Lacking a broad concept from Lozano, Beethoven's Seventh Symphony lost most of its shape under a head-splitting overdose of sound, particularly from the brass.

Among the guests at the concert, part of a celebration of the 36th anniversary of the United Nations' founding and a salute to the Organization of American States, were OAS Secretary General Alejandro Orfila, U.S. Representative to the U.N. Jeane Kirkpatrick, Secretary of State Alexander M. Haig and presidential counselor Edwin Meese. Haig conveyed President Reagan's regards in a welcoming address prior to the music.