I support Big Mick's suggestion of patching in a recorder to the Dennis Cook's board (with appropriate adapters). That should be better than any recorder located in the audience, which would pick up any sound in the immediate vicinity such as applause, scraping chairs, commentary, coughs and wheezes, shuffling papers, and choruses or refrains. The feed from the board would still not be as good as a studio recording but good enough to listen to if the performer were doing a good job.

Some inexperienced performers have a tendency to "roam" in the vicinity of the mic or to ignore it altogether!

It would also help if someone experienced monitored the recorder. Dennis has enough to do monitoring what people should be hearing in the hall.

Cheerily,
Charley Noble