It sounds like a vocaloid to me, but I can't really tell. Just been curious!. All of Emil's songs in NieR:Automata includes cues from the sacrifice track here and there. Hell, the Emil (Despair) track is straight up an. Print and download in PDF or MIDI Emil (Sacrifice). NieR Gestalt and Replicant OST I do not claim any credit.
From NieR: Automata Emil Sacrifice (Guitar Fingerstyle) Composers Keiichi Okabe, Keigo Hoashi, Kuniyuki Takahashi Tab by Clever Monkey. Stream NieR Soundtrack - Emil Sacrifice by Ricardo Gamboa 2 from desktop or your mobile device.