Adventures of the Little Mermaid (Saban, 1991)

Adventures of the Little Mermaid (人魚姫マリーナの冒険 Ningyo Hime Marina no Bouken, The Adventures of Mermaid Princess Marina) is an animated series produced by Fuji Television in the early 1990s, based on upon the Hans Christian Andersen fairy tale The Little Mermaid. This 26-episode TV series was originally a Japanese/French co-production created by Jean Chalopin and directed by Takehiro Miyano.

Song of the Sea Witch (Episode 12)
In this episode, Hedwig the Sea Witch gets her hands on a powerful hypnotizing flute (or pipe). The song it creates is said to be able to put anyone under control. This happens a few times to the heroine Marina and her friends.