I enjoyed very much this article about Riccardo Muti in the New York Times. He was in New York to conduct Verdi's Otello at Carnegie Hall. I was always told not to sing when conducting, but Muti appears to have another opinion.
It was followed by this review. I posted the picture because it shows the singers in a curious clump around the maestro. These are two very different perspectives, but without actually hearing the concert, it's impossible to judge. Perhaps the singers should be offered the opportunity to hear Muti sing their parts.