What exactly do you mean? Was it off the main stage, like stage left or stage right to where the main crowd couldn't see him do it? Or a mic like a background singer's mic?

If the mic was off the main stage, to where most people couldn't see it, my guess is that that was a mic to either the main soundman, or to the guy running sound for the stage monitors or side throws.. Side throws are fairly large speakers on each side of the stage that point across the stage and are intended for the bands to be able to hear themselves better.. I LOVE side throws!

In large productions you have a sound guy out front that mixes the sound for the audience and then usually a second guy off to the side of the stage (most of the time stage left, from my experiences) that mixes the onstage monitors and side throw mixes for the band to be able to hear themselves.. Those mixes, for the band, are just as important as the mix out front, cuz if the band can't hear themselves, things could get ugly.. Especially for singers..

So, to me, sounds like he had a mic setup to talk to whoever was running one of those 3 mixes: front/crowd, or monitor or side throw - or all three - in order to tell them he needed something adjusted, without the main crowd hearing him.... More than likely the guy talking also had an earpiece as part of the monitor system where he could be talked to by the sound guys, as well.. Normally, each band guy would just eyeball the guy mixing and point up or down for their instrument in the monitor mix.. then nod when the level was good for them..

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