Though not a great choice, it's often the only choice an opera company has in this situation, especially if there are no covers for the roles. There've been some doosies like this at the Pittsburgh Opera in the past few years, the most well-known of which was when the MAESTRO sang Radames in Act 3 of Aida because the singer was ill and his "sing-from-the-pit" replacement/lip-sync singer didn't make it to Pittsburgh in time for the show or even in time for Act 3 (flight delays). The original singer made a valiant effort and sang the first 2 acts, but was on the verge of literally ruining his voice, so the sound department quickly set up a microphone in the pit near the podium and the conductor sang the role with the original singer walking the staging and lip-synching. Honestly, opera audiences revel in this stuff. Much as a company doesn't want it to happen, many of the regular audience members find it fascinating - the reason to see live theatre.
And Jason Karn was in the young artist program at Pittsburgh Opera. I worked with him for several years there.
