Dragon Ball Z: Ryuuken Bakuhatsu!! Goku ga Yaraneba Dare ga Yaru

The Z Warriors discover an unopenable music box and are told to open it with the dragon balls. The contents turn out to be a warrior named Tapion who had sealed himself inside along with a monster called Hildegarn. Goku must now perfect a new technique to defeat the evil monster.

(Source: Anime News Network)