Requiem
English name: Anal Sanctuary
Genres: Hentai
Type: OVA, Episodes: 2
Aired: Jun 25, 2005 to Jul 25, 2005
Studio: Eshoya Honpo
Source: Visual novel
Rating: Rx - Hentai
Synopsis:
Based on a game by CLOCKUP 

Cannone is a violin that entrances people. Ceillia is a violin that was created by the angels that seals Cannone. 

Akio became a teacher for St. Cecillia Academy. He found Cannone sealed in the torture room under the chapel, he was fascinated by it's power. The other violin picked a girl to use it`s powers to steal Cannone. 

(Source: AnimeNfo)