tk_nz has a bunch of kanji for the mysterious performers, but since the booklet doesn't include a single one of them, I think they're probably just educated guesses.
T. HARADA = 原田大志
(Taishi Harada on Preprimer 1 & 2)
K. UEMURA = 上村かおり
(Kaori Uemura, viola de gamba player)
U. MATSUNUMA =
Yuka Matsunuma (I don't know how long she's been active as a musician but her credits all seem to be much more recent than this 1991 album)
H. YAMAMOTO =
Hiroyasu Yamamoto
S. SHIBANO = 柴野さつき
(Satsuki Shibano)
Y. NAKAMURA =
Yasuhiko Nakamura
S. OHASHI = 大橋真吾
(Special thanks for the OVA tracks on Falcom Special Box '90)
K. KYOYA =
京谷勝巳
G. OKADA =
Jiro Okada
M. TAKAGI = ?
S. NAKAI = 中井正剛
(Special thanks for the OVA tracks on Falcom Special Box '90)
T. WATANABE =
Takeshi Watanabe
K. YAMAMOTO = 山本寛
(Special thanks for the OVA tracks on Falcom Special Box '90)
I linked Nakamura, Okada, and Watanabe because they all worked together on Falcom Special Box '92 as well. Everyone else: yeah, maybe?