From 声(こえ) (koe, “voice”) + 変(か)わり (kawari, “changing, 連(れん)用(よう)形(けい) (ren'yōkei, “stem or continuative form”) of the verb 変(か)わる (kawaru, “to change”).”).
こえがわり • (koegawari) ←こゑがはり (kowegafari)?