A story too close to home...
Finbar Wright has sung Christmas concerts all over the United States for 12 years as part of the Irish Tenors. One night in Houston, things went a bit wrong.Sang it myself, way back in the day, and listened to a remarkable tenor and friend sing it throughout my life Christmas Eve. I still struggle not to not breathe at the crucial moments - which is the key to doing it well.
"We had a slightly older guest conductor and he had this kind of thing where he would sing very quietly with the singers," he said, laughing at the memory. "Over the general clatter of an orchestra and three tenors the audience usually couldn't hear it, but it just so happened on this night that the first violinist's microphone was very close to the conductor. He really loved 'O Holy Night' and started getting carried away, slightly out of tune and not quite hitting it. He got louder and louder until the first violinist broke down laughing. Then her neighbor started and next thing you know, the whole thing ground to a halt.
"Everybody took it in a great spirit. The conductor was very apologetic, and we just started it again. The funny thing is that the resumed performance had taken on a completely different life because suddenly it seemed like a special emotion had been injected into the whole thing. The humanity had been brought back into the divine." [More]
It ain't easy, so let performers know when it's done well.