female vocalist, with an intro I regret I can only describe as similar to “Puffin’ Billy,” the theme from Captain Kangaroo. (I’ve been thought all the samples at Amazon - sounds like it’s from the 4th Symphony)
I think you’re on the right track, going by your description. The opening movement of the 4th has what I presume is your Puffin’ Billy passage, and this reappears during the last movement, the one with the singer.
Edit: and if it’s the original song you want rather than its use in the symphony, it’s Das himmlische Lebens, about a minute into the clip.
Thank you GorillaMan!