Terpene cyclase that catalyzes the cyclization of farnesyl diphosphate (FPP) to various sesquiterpenes, including alpha-copaene, beta-copaene, beta-elemene, alpha-muurolene, gamma-muurolene and delta-cadinene. (2E,6E)-farnesyl diphosphate = alpha-copaene + diphosphate (2E,6E)-farnesyl diphosphate = beta-copaene + diphosphate (2E,6E)-farnesyl diphosphate = alpha-muurolene + diphosphate (2E,6E)-farnesyl diphosphate = diphosphate + gamma-muurolene (2E,6E)-farnesyl diphosphate = delta-cadinene + diphosphate The conserved DDXXD and NSE/DTE motifs are important for the catalytic activity, presumably through binding to Mg(2+). Belongs to the terpene synthase family.