I'm assuming that he got a full soundcheck earlier in the day, and just recalled what he had. The band was a cool setup, with a solid drummer and bass player, keyboard player, horn player, and male and female vocalists, the male leading 95% of the time.
The band started playing, and everything was tight. bass and drums were perfectly in sync, and mixed to prove it, the keys and horn player held down the melodies, and didn't fight each other. The lead vocalist started singing, and sat right on top. Things got a bit hairy when the girl jumped in, she really took over the mix. It was pretty obvious to me that she sandbagged in soundcheck, and now that it was show time, she was going all out, and was probably 9dB louder than soundcheck.
Kudos to the FOH guy for not jumping on her channel and frantically pulling her back into balance, but smoothly brought her down while brining the lead up. It was a cool non panic move. As the song progressed, i heard him dial in his verbs, and tweak them, and maybe some EQ changes on inputs, but really never straying from the bass/drum balance he had. That was his foundation, and he built nicely on it.
As the show progressed, I could tell he was in his zone and was paying more attention to effects, vocal delays when needed, all while not taking his attention away from the vocal balance. He nailed it all night. That first song was key to get things situated, and ensure a solid show.
Take time to go and be a punter at the local shows. In our area, there's free concerts with national acts happening Thurs-Sat, so when i have time, I go and check out not only some great bands, but some great engineers as well. Hopefully you can end up at a few in your area. Use your ears to learn their methods. After the show, offer congratulations on a job well done, and strike up a short conversation. Typically our little FOH guy club is pretty welcoming, and would love to shoot the breeze for a couple minutes before we have to go back to work and get the show back on the road.
Have fun, good luck, and don't forget the sunscreen.