Chamber orchestras vary in size, just as people do. A chamber orchestra may comprise as few as 13 (the smallest number that can sound like an orchestra) or as many as 20 string players, plus winds. A symphony orchestra usually musters a string body ranging upward from, say, 35 string players.

In between lies the clean, pliable ensemble of a classical orchestra. Two to three dozen strings nicely balance the dozen wind instruments called for in orchestrations of that period. Balancing instrumental sonority with orchestral economics to fill this neat niche, a number of fine classical orchestras have established themselves as important contributors to the world's musical scene.

Prague Philharmonia Orchestra

Oct. 28, Jiri Belohlavek conducting in Suntory Hall -- "Don Giovanni" Overture (Wolfgang Amadeus Mozart, 1756-91); Romance for Violin and Orchestra, Op. 11 (Antonin Leopold Dvorak, 1841-1904) featuring Masafumi Hori; Concerto No. 2 for Piano and Orchestra in F Minor, Op. 21 (Frederic Chopin, 1810-49) featuring Hiroko Nakamura; Biblical Songs, Op. 99/1-5 (Dvorak) featuring Roman Janal; Symphony No. 38 in D Major, K. 504 "Prague" (Mozart)

The 39-member Prague Philharmonia, founded by Jiri Belohlavek in 1994, was making its first appearance in Japan. The musical city of Prague and Mozart were forever linked in 1787 when the 31-year-old composer premiered there his most dramatic opera, "Don Giovanni," and composed his 31st symphony, known ever since as the "Prague" symphony.

The overture to "Don Giovanni" projected a genial atmosphere and sounded quite pretty and light. The meld of the wind instruments, seated in the old Czech Phil formation, was especially smooth and mellow, imbuing the sound of the classical orchestra with a gentle gloss.

Beolohlavek preserved the mellow, genial textures in Mozart's Prague symphony. He made the music sing, giving precedence throughout to the melody in the first violins. Mozart's music deliciously balances the cantilena with the infectious pulse of the inner rhythms.

With Hiroko Nakamura at the keyboard for Chopin's F-minor concerto, the primacy of the piano was never in doubt. Chopin's orchestration of his few works with accompaniment has generally been regarded as unskilled. Recent performances, however, have demonstrated that the composer's use of instrumental colors and textures was as ingenious and beguiling as Schumann's, if no less challenging to bring out.

Even though neither soloist was at all known to the general public, the most captivating portion of this program was the music by the great Czech composer Dvorak. Masafumi Hori was the sympathetic violin soloist for the Romance, a graciously orchestrated work of soothing loveliness. Baritone Roman Janal sang five Biblical Songs, all deliciously warm and far too short for their beauty.

Anima Eterna Orchestra

Oct. 25, Jos van Immerseel conducting in Suntory Hall -- Music from "Rosamunde," D. 797, "Magic Harp" Overture, D. 644 (Franz Peter Schubert, 1797-1828), Symphony No. 5 in C Minor, Op. 67 "Fate" (Ludwig van Beethoven, 1770-1827); Symphony No. 9 in C Major, D. 944 "Great" (Schubert)

The Anima Eterna Orchestra under Jos van Immerseel presented five performances during nine days in Japan. Founded by Immerseel in 1985, the 49-member classical orchestra was making its second appearance here since 1991, the Mozart year.

The meld of the AEO's lightly toned wind instruments, designed to replicate the instruments of the classical period, made a charming impression in Schubert's "Rosamunde" music and the overture. Immerseel paid special attention to the accentuation, which the composer wrote large in his manuscripts: sharp and heavy, lending a marked virility to the music.

Musical scholarship has recently tumbled to the fact that Schubert may have intended something different with these large-writ nuances, scrawled so large that they were long taken for diminuendos. The generous dimensions may have referred to duration rather than to decibels. Schubert was in all things a songwriter. In the human voice, accents sound more gentle than they do from an instrument, and they take perceptibly longer to produce and to decay. In a gracious vocal cantilena, where the singing line takes precedence over demarcation, the distinction between accent and diminuendo is delicately ambiguous.

In all this music, Immerseel took advantage of the light sonic mass of the classical orchestra to favor buoyant tempos flowing lightly, quickly and effortlessly -- particularly in Schubert's great C-major symphony. The sprightly flow of the long, soaring phrases was winning. Taken this way, with the delicate detail skillfully folded into the ebullient organism, it was possible to hear felicities which usually pass by unnoticed. The performance was fresh and exciting to hear.

When Beethoven turned to the recently invented metronome and his Broadwood pianoforte to specify tempos for his previously composed symphonies, he indicated speeds so lively that conductors simply ignored them, discounting them as impossible with large, full-bodied ensembles. The vibrant music of the great composer's C-minor symphony danced and sang delightfully in the light treatment, and the sparkling emotional ambiance was thrilling. The fine musical conception was complemented by very good playing.

It makes one wish that Immerseel could gather his specialist musicians from all over the world to perform as the Anima Eterna Orchestra more often. Once every eight years or so seems too long between visits.