Star earth is used in both video and audio recording studios.
The reason you would use a star earth would be for one reason. If you are using balanced equipment and are running cables over long distances (15 meters) then without a star earth every thing would end up with lots of hums and clicks.
As balanced equipment uses the earth as a reference then it is very important to make sure that the earth everywhere in a studio stays at absolute zero. This will mean that the reference voltage will be the same everywhere in the studio.
You do this by using another earth to physically bond everything that has a metal case together (Well sort of!)
You start with a main point then you spur off to other sections, you never return the cable back as that will create an earth loop (Which is bad, which is why ring mains are bad in a studio as they are effectively an earth loop).
You would make the desk your main point. Using a nice 4mm earth cable you would attach the cable to the desk making sure you have a really good connection. Your cable would then attach to an earth buzz bar and then from that point you can then spread off around the studio. If you have several main areas in the studio then you would put another earth buzz bar in each new position.
Every rack needs to have it’s metal rack strip earth bonded and ideally anything temporary in the studio needs to have a temporary earth fitted to it.