There is already an application that allows concert viewers to control the sound mix through their mobile phone so that they can hear their favorite instrument better. The app is called Peex Live and pairs up with the Peex rX, which consists of a headset connected to a radio wave receiver transmitted directly from the mixer.
This system has been used in the Farewell Yellow Brick Road, the final Elton John tour that started in the United States on September 8, 2018 and has over 300 concerts scheduled worldwide.
With no delay in sound (just as if it were heard live) and the ability to increase and lower the volume of the instruments depending on the listener's personal taste, this app also distinguishes itself by allowing a viewer to find a technically alternative feasible when you are in a location with poor acoustics or away from the concert hall.
The Peex rX wraps around its neck, resembles the audio guide devices used in museums, has only one on / off button and is fully controlled via the smartphone after pairing.
Incidentally, on the phone screen you can see an interface with five channels (guitar, voice, keys, bass and drums) with an intensity controller each allowing the user to adjust the sound that will reach the earphones.
Below is the official video that explains how the system works: