Complex sentence: He continued as music director and conductor until 12 December 1971, when a dispute between him and some of the orchestra's members resulted in his resignation backstage shortly before the start in order for the concert to continue under his baton.
Split into simpler sentences: He continued as music director and conductor until 12 December 1971. A dispute between Steinberg and some of the orchestra's members resulted in his resignation backstage shortly before the start in order for the concert to continue under his baton.