I was doing some tests...

This is the nerfed version. In the original KR patch, the circle buffs were tied to the buff you used with fantastic chorus. and they stacked.

So if you used Battlefield, a red circle would appear, one that gave out the debuff and battlefield. stepping in its radius refreshes both buffs, and those would stack if you also made an enduring chorus circle, which would give out an enduring and hymn buff.

Ours are only different in the fact that the rules for applying music buffs didn't change. it is a hard limit of one buff.