Technically speaking, poltergeists are not yuurei, but there are no other appropriate classifications for them so they are described here.

The youngest sister of the Prismriver Ensemble(*1), Lyrica Prismriver plays the keyboard and percussion.

Her body(*2) is the smallest of the three, but her music is dynamic.

Her appearance is no different from that of a human.

She is the shortest of her sisters, and thrashes about during live performances.

The keyboard she plays is said to be the yuurei of a synthesizer used by a famous artist that created sounds that were too peculiar so it never sold and faded into obscurity(*3), but it's unknown if this is true or not.

Her personality is the most human-like among the sisters, so she's easy to converse with.

However, she does have a sly, worldly side to her.

The sounds she creates are sounds that don't exist in the present world.

Her sounds are the sort of sounds one can't imagine where they came from or how they were created.

Rather than the yuurei of notes, one might say they're illlusionary notes.

Compared to her sisters' sounds, they are unlike anything heard before, but they don't resonate with the mind and spirit, and are heard normally with the ears.

Since they have no effect on the mind and spirit, you can listen to them without worry.

She normally performs together with her other two sisters.

If she ever acts on her own, she is probably quarreling with her sisters or has some ulterior purpose in mind.

1: See the article on Lunasa Prismriver.

2: Phantom or not, a body is a body.

3: They say this at the beginning of their live performances.

"She's so small it's hard to see her at performances, but hang in there, Lyrica!" (Anonymous)

She's small but her instruments are large, so she really doesn't stand out.

Hang in there.

"Is Lyrica ever going to hold a solo concert?" (Lyrica fan club member No. 1)

I can't answer that.

But I have never heard of her doing so.

"The other sisters are fine, but that Lyrica's a cheat. Her instrument can't be doing that." (Anonymous)

That keyboard somehow creates strange noises.

Nobody understands how it works, but that's how yuurei are.

She is very friendly to both humans and youkai, so you have nothing to fear from her.

You will probably never come across her on her own, but mutual understanding shouldn't be difficult, so you can avoid any danger by talking to her.

Also, poltergeists can't just sit still quietly.

So, even if they're carrying on or talking incessantly, they're not necessarily angry; just settle down and cope with it.

If you happen to cross her through some off chance, the best thing to do is retreat and run as if the death itself were after you.