LENOX -- It is generally agreed that if you can sing Mozart properly, you can sing just about everything else ever written for the trained voice; the opposite is not true.
The same observation is valid of orchestras: If an orchestra has the nimbleness of finger, breath, ear, and mind to play Mozart accurately, luminously, and with feeling, it can deliver superior Wagner, Strauss, Mahler, and Boulez; the opposite is not the case.
The Boston Symphony Orchestra celebrated Mozart's 250th birthday last weekend not just with ``Don Giovanni" but also with two other all-Mozart programs led by James Levine. There is no way the orchestra could've done this as well two years ago. Mozart was not a priority during the tenure of the previous music director, Seiji Ozawa. There have been only a handful of personnel changes, but today's BSO is not the same orchestra.
Friday night's program brought the ``Jupiter" Symphony, played with all the repeats, all the grandeur and intimacy, passion and precision. Mezzo-soprano Susan Graham sang the concert aria with piano obbligato, ``Ch'io mi scordi di te," with deep-burnished tone, ample flexibility, and vivid delivery of the words.
The evening's other soloist was pianist Richard Goode, but for this aria the bench was ably taken over by Levine. His shoulder injury and subsequent surgery have not impaired his keyboard skills.
Goode played Mozart's 27th and last piano concerto. Excesses of refinement at the beginning threatened to make the music evaporate, but as Goode settled down and dug in, he played with uncommon insight and depth -- and, in the finale, charm and spontaneity.
Sunday afternoon brought a solid and stirring performance of the Requiem, with some splendid singing from the Tanglewood Festival Chorus and a starry team of soloists, including a radiant Soile Isokoski (stepping in to replace Hei-Kyung Hong after finishing her performance as Donna Elvira in ``Don Giovanni" about 15 hours earlier), Graham, John Relyea, and an excellent lyric tenor making his BSO debut, Kenneth Tarver.
The program began with the amazing ``Posthorn" Serenade, music composed to be an entertaining diversion but that also rewards the closest attention. It might as well have been called the ``Woodwind" Serenade because of its prominent roles for solo piccolo, flute, oboe, and bassoon, all of them spiffily played.
The posthorn -- a valveless trumpet -- appears in only part of one movement, but it's a memorable, outdoorsy episode. In the solo by principal trumpet Charles Schlueter , not every note came out perfectly, but he did bring a glowing quality of tone to it, elegant dynamic shaping, and insouciant phrasing. Schlueter retires at the end of the summer, and this solo proved a jaunty valedictory address.