Ever wanted to know how Irish people wrote before they adopted the Roman Alphabet? This is the 'Ogham Alphabet' and its how the pre-Irish used to write. This book, the "Book of Ballymote". Nobody knows how old it is but its at least from the 1st Century BC
fol. 170r of the book of ballymote (1390), the uraicept na n-éces. explains the ogham script of early gaelic.
The oldest known musical composition featuring six-part polyphony, c. 1260 Sumer is icumen in, Lhude sing, cuccu; Groweth sed and bloweth med, And springth the wode nu; Sing, cuccu!