Eri is the singing voice of Sakura Kitaōji, Sora Kazesawa, Maria Himesato, and Kokone Kurisu.

Sora is a sexy-type idol. She sings in the medium-high range. She sounds very mature when she sings. She is part of the group Aikatsu8.

Maria is a cute-type idol. She sings in the high range. She sings very much like a baby would talk and squeaks a lot on her high notes. She is part of the group Aikatsu8. 

Sakura is a cute-type idol. She sings in the medium range. She also uses a fair amount of vibrato. She is part of the group Powapowa-Puririn.

Kokone is a pop-type idol. She sings in the high range. She has a lot of squeak and nasal in her voice. She is part of the group Sweet & Soft☆Nadeshiko. 
Sing at least 30 seconds of "Love Like Carmelize": https://www.youtube.com/watch?v=bjukG7Qz59Y

Keep in mind that if you are cast as Eri, you will need to sing as both Sora and Maria in Aikatsu8, so make sure their voices are distinct.