PRINCETON — Conductor Rossen Milanov has been making the Philadelphia version of the Grand Tour: Last week was Symphony in C in Camden, Friday was the Curtis (his alma mater) Symphony Orchestra at the Mann Center, and Sunday — most notably — was his end-of-season Princeton Symphony Orchestra concert at Richardson Auditorium here. In a program featuring Brahms' Symphony No. 4 and a new work by Princeton composer Sarah Kirkland Snider, Milanov stepped out from behind his image as dependable, congenial Rossen to become a conductor who wields demonic power.

First, the premiere: Snider has written a few different versions of the 20-minute, one-movement Disquiet with somewhat episodic results. But strictly from the evidence presented here (albeit in a somewhat tentative performance), she's a potentially significant voice on the American music landscape.

The idea of the piece is to explore the inner agitation beneath self-imposed composure — a promising prescription for harmonic layering that's successfully realized in any number of ways. Disquiet is framed by long-held string chords with pregnant two- and three-note motifs that germinate into events that consistently refuse to touch base with the usual emotional colors. Even a four-note trombone motif that might normally sound foreboding instead conveyed apprehension; it was followed by a shower of potentially ecstatic string pizzicato effects that instead conveyed a nuanced dose of anxiety.

Overall, Disquiet is packed with so many different kinds of details you wondered if it was three pieces collapsed into one — often a side effect with repeated revision; also, Snider's handling of the orchestra wasn't entirely confident. So this piece feels like the sort of rite of passage that prompts a mental note not to miss the next one.

Ravel's Piano Concerto in G, with Japanese pianist Rieko Aizawa (also a Curtis graduate, said to be Mieczyslaw Horszowski's last pupil), was notable for being what it so often isn't: an equal collaboration between orchestra and pianist. So often the pianist carries the piece while the orchestra interlocks only vaguely. Clearly, Milanov gave the concerto all the special attention it needed, allowing Aizawa to relax into it and make music, viewing the dreamy second movement through the lens of a Chopin nocturne, subtle rubatos and all.

Though Milanov's past Tchaikovsky performances have been full of fire, nothing he has done prepared me for his Brahms — except, perhaps, an unforgettable Philadelphia Orchestra performance given by the late Klaus Tennstedt in the mid-1980s. Milanov is too young to have been a Klauskateer (as Tennstedt devotees were nicknamed), so he obviously arrived at the terrifying intensity he displayed on his own. The first-movement climax might have been too big to top, but he topped it anyway in the final movement. There, this supposedly C-level orchestra rose to an A-level performance.

All the more fascinating: The contingent of 18 violins was smallish by modern standards but was what Brahms would have expected in his own time, and did not lack for lustrous tone. Thus, more details emerged in wind solos. Never have I heard so much poetry in the countermelodies. The end result: fewer musicians, more Brahms.

Contact music critic David Patrick Stearns at dstearns@phillynews.com.