If they are clairaudient and not imagination, by definition of clairaudience, they would explain themselves to the person that hears them. The bell signifies attaining a point of enlightenment and the ascention to a new understanding.

It is similar to an epifany, how could it not be known and understood if it's actually clairaudient? When it's imagination it won't be understood.

Enve, do you mean the orchestra, but then just before the concert begins where all the musicians attune their instruments? I read somethng about that at another post or tribe, don't recall exactly, someone mentioned hearing such a sound at times... Supertramp uses that in "The Fool's Overture", at the end of that song, and I love to hear that cacaphony of sounds! Actually in concerts it is the part I somehow enjoy the most --in a different way than Gergyev conducting Mahler's Titan which is a completely different aesthetic/ecstatic pleasure!-- and I always have found it odd that this "disphonic orchestra sound" touches me so deep... I really like it.

Maybe you got something here?

And oh, there is another sound that I mostly connect with concerts, during the breaks, when the audience has a coffee, and in this vaste space with its echo, all the people who murmur, speak softly and the sound of porcelain coffee cups and saucers and people stirring with these little metal spoons: tingelingelingeling... bells? right? Interesting conjunctions of sound....