The return of Mariss Jansons to the Heinz Hall podium for the final weeks of the symphony season is cause for rejoicing.

Presenting a concert of three masterpieces, Jansons and the orchestra demonstrate the growth they have achieved together in a richly rewarding concert.

The concert opened with the Musical Mystery, in this case a familiar overture that in turns was grand, exuberant and songful. Jansons led a delicious performance. Although there were a few sloppy moments, the orchestra had a flair recalling the charms of Sir Thomas Beecham.

Mozart's Piano Concerto No. 20. in D minor, featuring Czech pianist Ivan Moravec in a long overdue PSO debut. Moravec is a particularly interesting pianist, masterly as a colorist if he chooses, in Chopin and Ravel. In Viennese classicism, he shapes music with the sensibility of German intellectuals such as Schnabel and Serkin. He creates tremendous tensile strength in musical lines, with scrupulous voicing helped by an especially articulate left hand. Among his recordings, which include recent ones of Mozart piano concertos with Neville Marriner and the Academy of St. Martin In the Fields, two compact discs of Beethoven on the VAI label are especially stunning.

The Moravec/Jansons Mozart D minor was idiomatically dramatic yet ever sensitive to Mozart's gracious spirit. The many moods encountered even before the soloist enters were beautifully varied. Moravec, for all his strength, knows the value of understatement and how to build from it. His fingerwork was hard, though fluid, yet never more Beethovenian than Mozartean. Moravec also listens well and plays as sensitively with the orchestra as its members did with him.

Understatement had mixed results in the Romance, the second movement. The cool opening worked well, allowing Mozart's music to be become ever more affecting as it unfolded. But the tumultuous outburst drew too calm a response in this performance.

Fortunately, the fire of the finale burned hot before Mozart's coda presents emotional resolution to high spirits.

Brahms Symphony No. 2 in D major provided a triumphant conclusion to the concert. The performance was an impressive improvement over performances earlier in the season. String tone, which was thin at the opening concerts, is now full bodied. Textures arc now more transparent and therefore fuller. These qualities make Janson's interpretation more fully persuasive.

Melodic and motivic aspects of the first movement were presented with mastery. This is music after all that Includes Brahms "Lullaby" but is built with cunning as well as sentiment. String colors had a golden glow, from brightly lit high violins to deeply rich middle and lower strings. Yet the music is not all sunny, and Jansons brought impressive weight to marcato passages.

The second and third movements are contrasted yet shared beautiful wind solos. The depths of the slow movement were unhurried yet never ponderous. The light dance of third movement and its energetic contrasting sections were charming and poised emotionally.

The finale, despite not being as quick as Brahms apparently wanted, swept forward irresistibly. The big contrasting string tune had fabulous tone and feeling. Jansons had plenty of rhythmic kick for dynamic music and was aided by outstanding trombone playing in the coda, and not just in the big scale passages and sustained chord in the final measures.

The second half of the concert was a worthy continuation of the orchestra's distinguished Brahms's tradition. Individual and idiomatic, it was satisfying In itself and augers well for the future.

Jansons knows how to make every performance he conducts an occasion. He is revitalizing Pittsburgh concert life.

Mark Kanny is a free-lance music critic for the Post-Gazette.