A chorus of ghosts sounds like...

I was thinking about how to describe, in the stage directions for a play, the sound I would like the chorus of ghosts to make.

Here are some options:

"A Chorus of ghosts is heard...

1. Droning in a minor key
2. Chanting atonally
3. Droning atonally
4. Humming atonally in a minor key
5. Creating funerary harmonies
6. Creating an atonal but multi-layered harmony

"...sustained over a period of several minutes."

What's your vote?