{TABLE} Fidelio Overture ............. Beethoven Piano Concerto No 1 .......... Beethoven Symphony No 3 (Eroica) ....... Beethoven {/TABLE} THE new subscription season of the National Symphony Orchestra opened at the National Concert Hall last night at the heart of the matter, with an all Beethoven programme under principal conductor Kasper de Roo. All Beethoven concerts are among the most reliable box office draws, and, with Barry Douglas as soloist in the First Piano Concerto and the Eroica Symphony in the second half this one proved no exception.

Kasper de Roo's last offering of a Beethoven symphony (the Ninth, in May of last year) was not among his finest moments. The Eroica fared rather better, though it still seems to be the case that this conductor does not have the full measure of Beethoven's every note must count weightiness.

The effect in the Eroica was to lighten the first two movements, giving, if you want to take the title literally, an even keel heroism, Prozac low on inner tension. The later movements, in particular the Scherzo, had a sharper, more persuasive bite, and the horns here were happily in more secure form than they had been at some earlier points in the evening.

Firmly projected oboe playing (not something one hears; consistently from this orchestra) was an enjoyable feature of the second movement Funeral March, and, with a string section boasting 10 cellos and eight double basses, there was plenty of volume in some of the music's agitated climaxes.

The overture to Fidelio, which opened the concert, was, with its lighter air of extroversion, altogether more in keeping with the conductor's style.

Barry Douglas is not a player one readily associates with the early Beethoven concertos; his public persona as a musician is associated with music of altogether more romantic hue. Yet he approached the First Piano Concerto with a neat and stylish pianism, which is a sure in itself, and a preparedness not to ask of the piece more than it could yield.