Lullabies are often at the center of the most intimate moments between a child and their loved ones. A private space forms around singer and audience—a kind of temporary, invisible womb—in which begins what Spanish playwright Federico García Lorca called “a little initiation into poetic adventure.” Like magical incantations, these typically slow tunes, limited in melodic range, are transformative. As Lorca put it: “The mother transports the child beyond himself, into the remote distance, and returns him weary to her lap, to rest.”

Paradoxically, the lullaby is a uniquely adult genre. The musical simplicity allows for textual inventiveness, and it is a blessing, in many ways, that children cannot understand the words—as the lyrics often would do little to soothe young min...