(no subject)

I found this sentence in the Shaman King wiki:

A Vocaloid song titled of the same name was posted on Nico Nico Douga with the vocals performed by Megumi Hayashibara and lyrics written by the author Hiroyuki Takei based on the poem.

and now I am baffled. Megumi Hayashibara is not a vocaloid, she's a real human person (voice actress and singer, notable for roles such as Rei Ayanami and f!Ranma Saotome). Vocaloid songs are notable for not being sung by human people but instead by software; indeed I would argue that is their defining feature

i found what i think is the song being discussed and... it's described as a Hatsune Miku song? It sure sounds to my not very discerning ears more like a Hatsune Miku song? and yet the youtube link you can find there says, in the "music in this video" box, that the artist is 林原めぐみ. Which is how you write Megumi Hayashibara's name in Japanese.

who is singing the song? and if the answer is "vocaloid software", what is instead Megumi Hayashibara's involvement with it?

???