Another welcome proof of Mr. Schwarz's merits as a conductor could be heard at the Waterloo Village Festival in late July when Mr. Schwarz offered an evening of blockbusters: Hindemith's ''Mathis der Mahler'' suite; Falla's ''Nights in the Gardens of Spain''; Ravel's Concerto in G (the last two-mentioned with Miss de Larrocha as soloist); and Scriabin's ''Poem of Ecstasy.'' He got uncommonly fine sound out of this mostly student orchestra (the first-chair players hail from some of the best orchestras in North America). Interpretively, only the Hindemith could be faulted, and that for a lack of spiritual vision so crucial to the entire score, and a sense of musical movement toward a goal. The Scriabin was given an electrifying reading.
Miss de Larrocha's multifaceted talents were all on view in the Falla and Ravel. The rarely heard Falla is a work of uncommon beauty and evocative richness. The pianist presented it with restraint and much tonal richness. The Ravel, a sharper, wittier, occasionally jazzy piece, found the soloist in mercurial form, with a nice edge for the tarter moments, an understated sense of humor, and above all an impeccable grace in this unexpectedly graceful work.