An extensive collection of musical manuscripts - books of musical notation, described as Llyfrau Pricio. They have been roughly divided into five sections.
- Of a religious nature (name of compiler and date known) : consisting of manuscripts dating from the late 18th century to the late 19th century and owned by various individuals including, David Jones, Ty'n y Braich; Rev. E. Stephen, Tanymarian; Clygyrdy Mawr Family, Llangefni; John Maurice; Humphrey Jones; John Evans; Robert Owens, Ty'n y pant; John Williams, Llandderfel; Richard Williams, Cadnant; David Davies, Rowen; Gwilym Cowlyd and John Jenkins. They containing tunes , psalms, carols, anthems, hymns etc. composed by Ioan Rhagfyr; Griffith Griffiths; Hugh Jones; John Evans, Llanddeiniolen; John Ellis, Llanrwst; Rowland Eames; John Williams, Dolgellau; Dafydd Jones, Treffynnon; John Roberts, Henllan; Owain Alaw, Tanymarian; Ambrose Lloyd and John Morgan, Cadnant to name but a few.
- Of a religious nature (name of compiler and date unknown) : consisting of manuscripts compiled by various individuals including H. Williams; Thomas Hughes; Griffith Davies; J. H. Davies and E.T. Davies.
- Of a religious nature (collections) : consisting of the manuscripts of various individuals, including John Matthews; Hugh Morris; Rev. Roger Edwards; Rev. William Roberts; Thomas Roberts; Edmund D. Jones; Ellis Ylltyr Williams; Richard Hughes, Ty Hen Isaf; Gabriel Hughes.
- Secular tunes (folk tunes, minuets, marches, dances) : consisting of a mixture of manuscripts compiled or once owned by Maurice Edwards; John Llyn; Robert Thomas; Ellis Ylltyr Williams.
- Bob Owen, Croesor Manuscripts : consisting of manuscripts compiled various individuals including, Hugh Hughes; John Peter Factory; William Owen, Llanfrothen; Williams Griffiths, Beaumaris; Thomas Lewis, Aberffraw; Margaret Jones, Capel Curig etc.