In the circles of early music lovers, documented information about performance practice is so important as to be obsessively searched for by musicians and musicologists. While iconography sometimes cannot be relied on as evidence because of its symbolic meaning, a piece of information on the aesthetics of a performance, the making of an instrument, the composition of a group of instruments, or the repertoire performed is all the more valuable if it comes from a document, be it official or private, such as a letter. Considering that Isabella d’Este was a passionate lover of music and also a musician herself, it is easy to understand that the massive corpus of letters written and received by her can be an extraordinary mine of this type of information. Here the Anonima Frottolisti ensemble (TC490001, TC250001, TC400007) continues its research in a deep introspection into the meanders of the music of Humanism, focusing on a repertoire drawn from the letters of the Marquise of Mantua Isabella d'Este, whose strong cultural and artistic sensibility deeply marked her time.