I heard a lady talking about how they do it on radio 4 earlier, she says is takes a fully qualified signer around 30-40 hours to prepare for a show, just the main act the other problem being quite often the support act often isn't even announced until just before the show. Any genuine fans will know the words to the songs so maybe just a screen notifying the tracks would be good, this woman is just a Richard, She's not even into the band.