Works surprisingly well
Im in the music biz, a guitarist by trade. Play rock, hard rock, pop, Pop country, whatever is required. The key to having a great mix these days is to keep stage volume down as low as possible and let the PA system along with a qualified sound engineer handle the the front of house and then using fold back monitors or in my case "in-ear monitors to get the perfect mix I want to hear without affecting anyone else. The Apple Watch works great! I can read each instrument and vocals DB level right from the stage and track down the offending "too loud player" and show them the sound pressure that they are pushing off the stage with a number and level them out to a consistent level for the sound engineer. To work his/her magic. Good app, easy to use and you have hard evidence at how loud each player is with a db level so they can adjust. Good stuff!!
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Sharkey 5150 about
Decibel X:dB Sound Level Meter, v5.0.0