Bonta treats the womb's "song" with a mock-scientific, deadpan tone, as if he were describing a well-documented piece of music. He starts deep in evolutionary time, among bivalves and sea cucumbers, then piles on matter-of-fact details: it's best with a full orchestra, there are solo flute versions, it has rhythm and sheet music, and it can carry across long distances underwater. The humor comes from how seriously these odd claims are delivered, and from the exclamation about scientists, which sounds like a breathless news item.
The final turn is the funniest and most surprising. The womb itself doesn't even like this song. It prefers bossa nova and the occasional hymn to the Sacred Heart of Jesus. Suddenly the womb has its own taste and personality, separate from the "song" that is supposedly about it.
The speaker seems playful and amused, but there's tenderness underneath. The mood is light, whimsical and slightly absurd, while still hinting at something ancient and sacred about where life begins.