Brace yourself! It’s Icelandic composer Jon Leif’s “Saga Symphony.” Scored for tuned anvils, stones, whip, shields of iron, leather, and wood, great wooden containers played by large hammers, and six ancient long horns, or lurs, the work is an intriguing blend of extravagance and austerity. We greet our fate with courage and stoicism, this Sunday at 10 pm.