Looping Sound from an Empty Prim

Perhaps this is a well-known effect, but it took me by surprise.

I used llLoopSound on a sound stored in a prim, then decided against it.
I deleted both the script and the sound from the prim's contents.

But the sound looped on, every time I rezzed the prim, even after relogging!

Of course, llStopSound terminated the phantom sound, once and for all.

Does this mean that each prim has a persistent looped sound property set by llLoopSound, similar to the persistent sit target set by llSitTarget?

Yep, I believe a Looped sound is a prim property. It has to be, because once the statement is executed, it is supposed to be persistent.

Not sure if it's a bug or a feature, but that's been my experience too.

Be advised that like a few other persistent properties of this type, shift-dragging a copy kills it too.

Yep. That's because the prims in the copy so made are brand-spanking new. Sadly, no "hidden" prim properties are copied in shift-drag.