The Grand Maestro's Orchestra

You summon an illusory orchestra at a point within range, the appearance of which is determined by the caster. The orchestra takes up a 10-foot diameter circle on the ground but is completely intangible. The orchestra begins playing music as soon as they are created and this music can be heard clearly by any creature within 120 feet of the orchestra. While the orchestra plays, each creature you designate that can hear it, gains a d12 die at the start of each of their turns. A creature with this die may add the it to any attack roll, saving throw, or ability check they make before the start of their next turn. Alternatively, the die can be expended and rolled to gain the rolled number as temporary hit points. This die does not stack with Bardic Inspiration or any similar abilities.