Seasoned concertgoers know what they're in for at a Prokofiev/Shostakovich program, though not this week: The Philadelphia Orchestra's Friday concert at the Kimmel Center showed both composers far out on distant artistic limbs, Prokofiev with his

Piano Concerto No. 2

and Shostakovich with his

Symphony No. 4

. They retreated,

but what fascinating acts of artistic brinksmanship these two works are.

Both have history here: In 1963, Eugene Ormandy gave the U.S. premiere of the Shostakovich, which the composer had held back for 26 years for fear its modernity would get him in trouble. Even so, one never gets used to these pieces. They can seem like a jumble of unrelated musical events, easy to connect with momentarily, but what on earth are they doing together? Prokofiev's concerto attempts musical Cubism with angular edges and multiple viewpoints rather than a linear narrative.

Yuja Wang has been the Prokofiev concerto's charismatic champion, and she was missed on Friday. Though Yefim Bronfman has some of the sturdiest fingers in the business, he took a classicist approach to the piece's percussiveness, emphasizing the constructive elements more than the depth of content. The melancholy of the opening movement and delirium of the third movement felt conspicuously absent. Luckily, music director Yannick Nézet-Séguin's vividly colored accompaniment found a near-operatic drama in the piece's narrative.

That approach went further with the even wilder Shostakovich symphony, which seemed peopled with characters speaking through instruments rather than voices - the composer's history accompanying silent movies being one explanation. But the main challenge of the piece is following its compressed sense of invention. The first movement is full of thematic connections (often hinted at more than stated), but the final movement gives mere transitional passages expanded lives of their own amid the quirkiest of marches, waltzes, and other thoroughly unexpected terrains. No heroes or aristocrats are conjured by this symphony. We're talking peasants, folk musicians, and shady street people.

Nézet-Séguin's characteristic talent for building long-term symphonic arcs was put to crucial use here. All of the symphony's alcoves had their place, but with an effect that was never unduly tidy. So often, the soul of any Philadelphia Orchestra performance comes from the incidental solos, but that was especially the case here: They were played so that you all but saw the characters' faces. But the performance also had plenty of shock value. In contrast to Ormandy (who recorded the work), Nézet-Séguin is long suspected to have a radical streak. I heard it on Friday. And I hope to hear it constantly.

Additional performance: 8 p.m. Saturday at the Kimmel Center, Broad and Spruce Streets. Tickets: $50-$157. Information: 215-893-1999 or philorch.org.