From the gently sloping approach path, the William M. Lowman Concert Hall rises into view through a screen of tall pines at the Idyllwild Arts Academy. At first glimpse, the hall’s reddish-brown cladding resembles the wood buildings that dot the surrounding rugged terrain, high in California’s San Jacinto Mountains. This 205-acre property was once a summer camp. And though it evolved, about 30 years ago, into a professional-caliber boarding high school for the performing and visual arts, the campus has retained its original rustic character. But as you near the new concert hall, you realize its cladding isn’t wood but pleated weathering steel, and the building’s quiet complexity begins to reveal itself.

The facade—an irregularly faceted sheer face with a mountainlike roofline silhouette—echoes Lily Rock, the massive granite outcropping in the background. In designing the hall, Los Angeles–based Sander Architects (SA) cut back dense growth to reopen sight lines to this natural monument in the landscape; the designers also borrowed the rhythmic cross-section of folds across the hall’s rusted skin from the ascending and descending notes of a musical score. Yet virtually nothing about the building is an indulgent or purely poetic gesture.