Volume Seven of the Catalogus fragmentorum cum notis musicis medii aevi in Slovacia series provides access to the oldest materials of the Slovak National Museum – Betliar Museum. Eighteen notated and twelve (plus two) non-notated parchment bindings from the twelfth to the fifteenth centuries have survived in the bindings of books in the Library of the Betliar Mansion. Manuscripts of various contents and provenance were used as the upper cover of younger books. All the notated sources document monophonic liturgical chant, the so-called cantus planus, or plainchant. This is the first time within these series that notated and non-notated fragments have been processed together. The palaeographical and contentual (liturgical and musicological) analysis of the fragments has revealed either the transfer of musical codices from the place of their origin and use (manuscripts from Bohemia, Germany, and Poland) or the local specificities of Hungarian scriptoria (manuscripts from Spiš).