No doubt the music has been used in so many movie soundtracks that you could easily believe Vivaldi is suitable anywhere. Also, its popularity implies that it can't be hard to perform. Not so, since the early-music world has shown in recent years that Vivaldi no longer feels repetitive and second-rate when his manic energy is given full rein. So even though The Four Seasons seems closer to home in the semi-outdoor Mann Center, the Philadelphia Orchestra's middling tempos and fitful momentum on Wednesday went halfway back to the bad old days.

Not that conductor Lio Kuokman, one of this week's guests from the Curtis Institute, was necessarily behind the Vivaldi performance-practice curve. There were so many places he wanted to go, so many side roads to explore, that tempos couldn't help but bog down, even while he added tasteful embellishments doubling on harpsichord.

Kuokman had a greatly capable soloist in 14-year-old violinist Yu-Chien Tseng, also from Curtis, whose intense feeling for the piece's purely musical value made its descriptions of natural phenomena secondary. Still, the four concertos came with such episodic sameness under the conductor's watch, you had to follow your program to be reminded where you were in the piece. Next to real-life nature, Vivaldi's portrayal seemed disorientingly slow. Yet the performance didn't diminish one's interest in future efforts by these artists. The inquisitive meticulousness that felt wrong here could be a plus in other repertoire. Also, violinist Tseng clearly has wide possibilities in his future.

The second half of the program, led by associate conductor Rossen Milanov, included the orchestra's first performance of Rainbow Body by the 41-year-old Texas-born composer Christopher Theofanidis, a neo-tonal composer whose reach stretches back to 12th-century poet/composer/abbess Hildegard of Bingen. Her music is adapted in Rainbow Body - and so recognizably that this longtime Hildegard admirer was momentarily giddy: This once-obscure figure is being heard by a large Mann audience! And though her vocal chants were refracted by Theofanidis in a large orchestra, none of the spiritual charge was lost. As a whole, Rainbow Body doesn't hang together but has such compelling moments that it is entering the orchestra repertoire - and certainly that of Milanov, who has championed it with New Jersey's Symphony in C.

At the concert's start, the audience was invited to vote via text message on the choice of encores - though the choice element wasn't significant. Stravinsky's Firebird Suite, heard in a particularly fine performance at the close of Wednesday's program, was fated to be followed by one of two Sousa marches. "Washington Post March" won out. Stravinsky next to Sousa? The close proximity to July Fourth didn't make that juxtaposition any more sensible. There are times and places for Sousa - lots of them, such as neighborhood concerts where general audiences drop in, or pops concerts where mixed programs are expected. However, this was an audience that traveled to hear the Philadelphia Orchestra, which normally needs no anti-elitist apologies implied by a Sousa encore. It's true that audience response was rousing - but that's what Sousa marches do, even in transcriptions for symphony orchestra that take away their edge. The odd part is that Milanov participated in this suspect enterprise - unless he's after Peter Nero's job.