In Iranian classical music the vocalist is the raison d’etre—the instrumentalists are crucial, but in general, they’re present to provide meticulous, carefully modulated and strictly regimented support for the singer. The Dastan Ensemble’s skill explains why they’ve been chosen by heavy duty singers like Parissa, Shahram Nazeri, and Sima Bina as accompanists, but they’ve worked hard to establish an instrumental tradition. On last year’s Dastan Instrument that’s just what they did, showcasing original material without a vocalist in earshot.

The thing is, the brilliance of the group—presently Hamid Motebassem on tar and setar, Pejman Hadadi on percussion, Saeed Farajpouri on kamancheh, and Behnam Samani on percussion—comes through loud and clear when they work with singers. The group performs tomorrow night at the Ryan Auditorium (2145 Sheridan) on the campus of Northwestern University in Evanston at 8 PM in support of Endless Ocean (Ava Korshid), a stunning new album with singer Salar Aghili. The singer and the ensemble form a dazzling union, each instrumental passage so inextricably linked to his vocal lines that Dastan is doing a whole lot more than just backing him up. The members get plenty of space to improvise—although it’s always within the rigid parameters of dastgah, the system of modes that organizes Persian classical music—but the greatest pleasure for me is basking in their precision, group sound, and the way they convey serious emotion using clusters of notes within tight intervals.