Of the medieval music manuscript discoveries of the recent past, one of the most unexpected and intriguing has been the palimpsest volume discovered at the church of San Lorenzo in Florence in the early 1980s. Manuscript 2211 of the church of San Lorenzo now bears the title “Campione de Beni del 1504” and details the acquisition and rental of properties up to and beyond that date. Interest in the San Lorenzo Palimpsest stems from the fact that all of its present 111 parchment leaves reveal traces of its original function: in the first decades of the Quattrocento the volume was compiled as a sizeable collection of ars nova and early fifteenth-century polyphony. Many decades later, the music manuscript was unbound, its leaves scraped clean of music and text, and then most of the source was assembled and bound as it began its reincarnation as an administrative ledger. The use of multispectral imaging has produced previously unimaginable results in going well beyond what had been possible, allowing for outstanding visibility in the final enhanced published images. This two-volume publication, including an introductory study and pseudo-color images, constitutes the virtual recovery of a lost codex, offering readings of its original musical content that make possible further scholarly study. The music collection contains more than 200 songs, among them those of known Trecento composers such as Jacopo da Bologna, Francesco Landini, Paolo da Firenze, and Antonio Zacara da Teramo.