Koe

koe: (1) voice


声 -- n.

Example: Tiger and Bunny had a character song called 'Seigi no Koe ga Kikoerukai?' which you can translate as Can You Hear the Voice of Justice?

Kokoro

kokoro: (1) mind (2) heart

心 — n.

Where to find: have you ever heard the phrase ‘kokoro no tomo’? It was pretty oldie song.