There were loud cheers after a curious and charming concert by the National Gallery Orchestra last evening.

The curiosity was a Concerto for Piano Four-Hands by Carl Czerny, a playful romp in C major that was new to these ears if not to these parts.

Czerny is better known to all piano students as the creator of ever so many after-school exercises, and the concerto was full of remembrances of drills past. In it, the composer actually captured some of Beethoven's elegance, if not his substance. And the work's demands for equal parts of musicianship and atheleticism found it not without a few echoes of P.D.Q. Bach's Concerto for Piano vs. Orchestra. It was fun.

Jean and Kenneth Wentworth were the soloists, hovering over each other's hands and lighting some real fires on stage. If their four hands at times danced over the keyboard with the pianistic equivalent of two left feet, the effect was ultimately dynamic and quite effective.

The program opened with Richard Bales' own "Homeage to Giles Farnby," a transcription for strings of pieces from the Fitzwilliam Virginal Book. It was a set of seven shamefully anachronistic, sinfully entertaining musical scenes full of those romantic melodies that so often pose in baroque garb. The strings of the National Gallery Orchestra played with a welcome sheen not evident in last weeks's concert.

Beethoven's almost pastoral Symphony No. 4 was given full-bodied treatment, as much a result of the deceptively generous acoustics of the East Garden Court as Bales' elegant conduction.With a cheering standing-room-only crowd, it seems lately that of all the attractions in the National Gallery, the orchestra is fast becoming the most popular.