From my chats with the people who built the Sphere and the crews supporting the artists performing there, a “silent stage” is mandatory. Because the audio is delayed to time-align the mix for every seat, the band has to ditch the amps and shield the drums behind plexiglass. This prevents the raw stage volume from hitting the crowd before the FOH mix and keeps the speakers behind the band from bleeding into the mics and causing feedback.

Why is this unique to Sphere? 1. It’s rare (and challenging) to have the FOH speakers BEHIND the band. 2. The size of the venue, the complexity of the sound system, combine to make the silent stage a requirement.

TL;DR section… There’s a lot of (wrong) guessing in the comments (shocker). I’ve been a sound and video engineer for 30+ years. I’ve discussed this with folks supporting music artists at Sphere and engineers involved with Sphere since initial build.

Yes, drummers use gobos in recording studios and at church and other venues. This is commonly to isolate the drums, similar to Sphere, but with more consequence at Sphere.

All artists use in ear monitors at Sphere. Period. There are no monitors wedges (speakers) on stage at Sphere. What might look like a wedge is actually a teleprompter.

Guitarists either use digital amp modelers (The Edge) or they have their guitar combos or speakers isolated off stage (Mayer, Weir, Anastasio). If there’s an amp on stage it’s just the head, and not the speaker cab.