Vigorous applause from a seriously underpopulated audience greeted the first Symphony Hall performance by Boston Symphony Orchestra assistant conductor Jens Georg Bachmann last night. This response was not matched by comparable signs of enthusiasm from the musicians.
It was possible to understand and even to feel opposing responses. It was a creditable performance, and if Bachmann were 23 one would be excited at his promise; he's 33, however, so there are things to worry about. He boasts a pleasant stage presence, at once eager-beaver and authoritative, and conducts with broad, flowing gestures that are nearly always pertinent.
The German conductor chose an all-German program composed by Weber, Schumann, and Mendelssohn between 1826 and 1845. As you would expect from a protege of music director James Levine, all the pieces sounded different and individual, yet also connected to the same pervasive Romantic-period impulses. His tempos were lively, well-chosen, and convincing, but his rhythmic sense seems to be less keen. Passages in Weber's overture to the opera ''Oberon" and in Mendelssohn's ''Scotch" Symphony that were both slow and quiet tended to lose backbone, and not every transition avoided whiplash.
Still, the famous melody in the slow movement of the Mendelssohn soared sumptuously enough and there was deft work from the quartet of solo woodwinds, especially clarinetist William R. Hudgins. But too much got too loud too fast, and stayed that way for too long. There wasn't much refinement of detail and balance and sometimes the orchestra sounded rough and not absolutely in tune.
The soloist in the Schumann Piano Concerto was Andreas Haefliger, who has become an A-list artist for the classical and early-Romantic repertory. Familiar and well-loved as it is, this concerto has become difficult to cast in recent years and some very prominent pianists have come to grief in it, including several at the BSO. The exceptions were Nelson Freire, who made it work at Tanglewood, and Dubravka Tomsic, who played it captivatingly with the New Hampshire Symphony.
Haefliger has a profound musical intelligence and made some unusual choices. Schumann was only 31 when he wrote the concerto, and newly married to his beloved Clara. Haefliger went all out for youthful impetuosity, passion, and speed. He began excitingly by making no visible preparation for the downward cascade of chords that introduce the piano -- most pianists carefully set themselves in position before taking the plunge.
But the impetuosity came at the cost of warmth of tone and feeling, chamber-music interplay, and an element of caprice -- qualities equally essential to the music. The speed made it difficult for Bachmann and the orchestra to place their punctuation marks with absolute precision. Important oboe solos were assertively loud and out of tune; when Levine is present, Keisuke Wakao plays with discipline and artistry; when he is not, elegant and musical Dr. Jekyll makes way for Mr. Hyde.