I'd like to expose my young children to the sounds of Japanese at night as they go to sleep. Specifically, I'd like to play Japanese lullabies or other soothing music with vocals. Where do I find such music?
I know a children's song, かえるのうた (The Frog's Song, The Frog Song) I'm not sure if you'd classify it as a lullaby, but it has a simple melody and can even be sung in a round (I think of it as the Japanese "Row, Row, Row your Boat")
Here's a link: Frog Song
Note: There seems to be a regional difference where the line "Gero gero gero gero" is replaced with "Kiki kiki kiki kiki".