The wedding singing went well, although I was a nervous wreck up until the moment of the actual singing. (In truth, I was pretty cranky for two or three days beforehand.) However, no one seemed to care or even know about my made-up part of the responsorial, including the priest.
It's just too bad that they didn't feel like singing along to the chorus that was already in the songbook. I think one guy in the entire congregation sang along. (Instead of making up the verses only, I could have made up the entire thing and it would have turned out about the same.)
At the reception, several people individually felt compelled to tell me they felt guilty about not joining in on the chorus, but felt they should leave me to do the singing. In other words they were chicken!
A goodly number of people also mentioned getting goosebumps during the Ave Maria. As a good clinician, I should have inquired about other symptoms such as nausea, shaking, hot flushes, heart palpitations, chest pain, a sense of suffocation or choking, and other symptoms of anxiety. However, I forgot to do so in my relief at having finally finished.
The bride has since reported that scores of people have been asking her if I "do weddings". But you know, I tried all that before grad school, and it didn't go anywhere. At least I don't have to sing at my own wedding, as Argotnaut did at hers. Sheesh! Talk about piling on the pressure.