Yesterday I was also down in Kent visiting my landlady and landlord from when I started teaching and meeting up with my friend from Austria who was a language assistant then.
Burgi (aka Notburga) is a pretty serious singer when not teaching English and Spanish and we got talking about what you have to do when you are not enjoying a performance. This was on the back of two performances she had just done of 'The Creation.' Even the stamps have Haydn on this year. Her Choir had hired a very famous soprano - so famous in fact that I have heard of her. I was very impressed to hear she was singing with such a top name. But it turned out that the lady in question had not been singing for about three months after an operation and her performances were dire. Terrible tone quality, unclear diction, out of tune and out of time. Oh and no phrasing either.
Burgi said that all the while she studied the faces of the orchestra and they betrayed nothing. She said there was almost an audible gasp from the choir whe she first sang. We decided that you have to focus on something else when either the soloist or indeed the music is not working the magic. You can just focus in on your own playing, or the mechanics of accompanying carefully or indeed any number of things that mean that you are actually engaged in the music and really trying to do it well. Tough stuff if the soprano soloist should really be indisposed and someone needs to be phoning round for a dep.