Ogre -Grand Repeat-
Artist: 市ノ瀬洋一 (chorus performance) =
Yoichi Ichinose
Source 1 (Tenor voice. Credited alongside Yasutaka Anzai and Risa Oki [Lisa Ooki])
Source 2 (Profile page of Voice Field inc.)
Only Yesterday Image Album
Artist: 大野祥孝 (clap) =
Yoshitaka Ohno
Source 1 (Credited as Music Coordinator in an album in which Katz Hoshi also collaborated.
Another example of the same)
About
R246の車達, I have no idea what or who is.