The medical problems of conductor James Levine have had two major American musical organizations, the Metropolitan Opera and the Boston Symphony Orchestra, on pins and needles. He’s the music director of both, and his ailments have led to quite a few cancellations lately.

On Tuesday, in obvious response to the situation, the Met named Italian conductor Fabio Luisi as its principal guest conductor. Only the second person ever to hold the position, Luisi has substituted for Levine this season in performances of Tosca and Lulu and will play an increasing role in the company for at least the next three years.

Levine had lower back surgery this month, and in recent years has had herniated-disk and rotator-cuff surgery and undergone the removal of a cancerous kidney cyst.