CINCINNATI — “I am known for writing very dark, disturbing music,” the composer Christopher Rouse, who died last month at 70, once said. “It just happened that every time I had a piece to write, somebody died whose death had a big effect on me.”

When the time came to write his Symphony No. 6, which received its posthumous premiere on Friday with the Cincinnati Symphony Orchestra, he again returned to the subject of death — though, as he wrote in a program note typed from bed in hospice care, “in this event it is my own.”

Mr. Rouse — one of the great American composers of our time, admired by audiences and fellow artists alike — had been suffering from renal cancer, and treated the symphony as his final musical statement. He typically signed off his scores with the Latin phrase “Deo gratias,” or “thanks be to God.” But under the final bar of the Sixth Symphony, he wrote “Finis”: the end.