This study explores the context for a small monophonic Latin song preserved in an eclectic Italian anthology manuscript produced around the turn of the fifteenth century. The song bears the Italian heading L'antefana di Ser Lorenzo, and is presumably connected to the Florentine composer Lorenzo Masini. “Diligenter advertant chantores” (as the Latin text begins) attracted considerable attention when it was first made widely available in facsimiles of the mid-twentieth century. Scholars of late medieval music, confronted by the song's apparent intellectual virtuosity and the diabolical excess of its so-called musica ficta signs, drew the conclusion that its musical context lay hidden within the history of music theory and perhaps even in its most esoteric corners. But repositioned against a new and still-emerging understanding of the pedagogical practices of the ars grammatica and ars memorativa, L'antefana takes on a different sort of historical significance. Details of its previously neglected text and the evidence of its fantastical notation suggest that it is a simple riddle intended for the youngest singers, likely a learning game of a very rudimentary sort (one of several considered in this article). Such classroom amusements still remain childhood constants, bridging the supposed gap between medieval and modern musical lives.