歌うたい出だす

godan verb (-su), intransitive verb

break into song; burst into song; begin singing

Describes the spontaneous or sudden start of singing. Often used when someone starts singing without prompting or when a group suddenly begins to sing.

• 彼かの女じょは突とつ然ぜん歌うたい出だした。

  She suddenly burst into song.

• みんなで一いっ緒しょに歌うたい出だそう。

  Let's all start singing together.