Three new works, a hot young Slovenian violinist, plus Mozart's Symphony No. 35 could have, would have, and should have added up to an impressive season finale for the Chamber Orchestra of Philadelphia Sunday at the Kimmel Center. But they didn't quite.

This is the year music director Dirk Brossé emerged from the more constricted repertoire of past administrations. But the new-music programming, however attractive, didn't come close to holding its own alongside the established works.

Brossé's own 2009 violin-concerto-of-sorts, titled Echoes of Silent Voices, is an earnest piece dedicated to Holocaust victims and certainly has a place in concerts surrounded by like-minded works. But the Mendelssohn Violin Concerto came before it, establishing a standard. Mendelssohn knew exactly how much mileage can be expected from any given theme group and transformed it into dynamic narratives. Brossé's five-note theme arrived time and again, perhaps intending to be mesmerizing with different orchestral backdrops. By the end, though, the theme felt like a bad penny that wouldn't go away.

Salvatore Di Vittorio's Venus and Adonis was basically an orchestra song, and often a beautiful one, with a finale that felt like the sound track to an absent movie. Mendelssohn's more concentrated melodies, in comparison, say much more with far fewer notes. Nick DiBernadino, still a Curtis Institute student, wrote a short scherzo titled To The Colors that needed to be part of something larger.

Of course, new pieces can't always have the confident performances of familiar works. Even so, the new works, with the exception of Di Vittorio, were under-rehearsed. Even the program's other big classic, Mozart's Symphony No. 35 ("Haffner") lacked a degree of polish and security that suggested extra rehearsal is essential for Chamber Orchestra to maintain its standing in the community.

Brossé was full of bold, personal interpretive ideas - more than in some of his past outings in this period of music - that needed more fully realized execution for maximum impact. Violinist Lara Trotovsek luckily had a good accompaniment in the Mendelssohn concerto, in a reading that began in a business-as-usual fashion but connected increasingly with the music, shading the concerto with darker colors and bringing out other dimensions to the composer's ardent spirits. She's an emerging voice to watch. The performance didn't blaze (Mendelssohn is too polite for that) but clearly smoldered.