This 一覧 is, and will always be, incomplete. Please feel free to contribute によって adding utaites, their romaji and hiragana name, what sort of singer they are and their gender.

96neko/96猫 - Female (Ryouseirui)
Che:Sakurai/che:櫻井 -Female (Ryouseirui)
Choucho/ちょうちょ - Female (Professional)
clear    /クリア - Male
Cocolu/ココル - Female (Ryouseirui)
Dasoku/蛇足 - Male
Gero/げろ - Male
Glutamine/ぐるたみん - Male
Hanatan/花たん - Female
Hitori/ひと里 - Female (Ryouseirui)
Jenga/ジェンガ - Male (Ryouseirui)
Kogeinu/コゲ犬     - Male (Ryouseirui)
Lon/ろん - Female
Mi-chan/みーちゃん - male
nano/ナノ - female (Ryouseirui, Bilingual, Professional)
Nero    /ねろ    - Male
Piko/ピコ - male (Ryouseirui, Professional)
Pokota/ぽこた - Male
Ritsuka/リツカ - Female
Sekihan/赤飯 - Male (Ryouseirui)
Senka/染香 - Male (Ryouseirui, Inactive)
ShounenT/少年Ｔ - male (Professional)
Soraru/そらる - male
Tourai/トゥライ - male (Inactive Utaite, Professional Composer, Ryuusei-P)
Touyu/灯油 - Male (Ryouseirui)
Usa/うさ - Female
Valshe/バルシェ - Female (Ryouseirui, Professional)
vipTenchou/vip店長 - Male (Ryouseirui)
Wotamin/ヲタみん - Female
Yamai/ヤマイ - Female