It would seem a contradiction to observe that Richard Bales' concerts with the National Gallery Orchestra tend to consist, commendably, of works unlikely to be heard elsewhere in this city, and then to suggest that the orchestra's programming is less than adventurous. This is not to carp that there is little variety; it is only to say that the stylistic range is narrow, and can lead to too much of a good thing.

For instance, the four works at last night's concert varied from the seductively ingratiating--Poulenc's Piano Concerto of 1950--to the well-meaning but academically shallow--a short episode for oboe and orchestra called "The Winter's Passed" by the American composer Wayne Barlow, who is celebrating his 80th birthday. There was also the Mendelssohn First Symphony and Sir William Walton's music for Olivier's film of "Richard III" (in observance of Walton's 80th birthday).

What all these works share is their commitment to a direct, conservative melodic and harmonic idiom. It is also the Bales idiom.

In the Poulenc the result is quite sophisticated. The concerto starts with a piano tune in an octave that sounds more like a tender Piaf ballad than the start of a concerto. It is lovely and sounds authentically of the boulevard, but what is it doing here? Yet before you know it Poulenc has mixed it into his spicy blend. There is a similar incongruity in the main theme of the slow movement, where the melody sounds like the most thunderstruck Rachmaninoff until Poulenc punctures its pathos with Parisian wit. Pianist Robin McCabe played stylishly.

The Walton is limited by its use of Elizabethan conventions. But it is Shakespearean mood music, and as such is excellent.

In the inner two movements of the Mendelssohn, the young composer is trying to imitate early Schubert, and comes remarkably close. In the outer movements he is shooting for his later symphonies, and falls farther short. Throughout the evening the orchestra was strong on e'lan, if not on nuance.