Ranma ½: Nettou Uta Gassen
English name: Ranma 1/2: Hot Song Contest
Genres: Comedy
Type: OVA, Episodes: 2
Aired: Nov 7, 1990 to Nov 21, 1990
Studio: Kitty Film Mitaka Studio
Source: Manga
Rating: PG-13 - Teens 13 or older
Synopsis:
A two-part music OVA series never released outside of Japan featuring the main Ranma 1/2 characters. They appear to be having a music contest at a local TV station. As everybody knows, these characters can't get along for more than three minutes and hilarity and hijinks ensue. 

(Source: AniDB)