The main reason there is no written record of Irish music prior to 1100 has to do with the systems in which the music was taught and performed:
The pre-Christian Irish had their ogham music-tablature, and the Irish of the seventh-eleventh century had the neumal accents, after which the Guidonian system was adopted The Guidonian hand was known in Ireland at the close of the eleventh century
Ogham = An ancient British and Irish alphabet, consisting of twenty characters formed by parallel strokes on either side of or across a continuous line. The very word ogham suggests at once a musical signification, and, therefore, it is of the very highest importance to claim for Ireland the earliest form of musical tablature.
http://www.claddaghdesign.com/blog/history/a-guide-to-the-ogham-alphabet/
A neume (/ˈnjuːm/; spelled neum in, for instance, the Solesmes publications in English)[1][2][3] is the basic element of Western and Eastern systems of musical notation prior to the invention of five-line staff notation. The word is a Middle English corruption of the Greek word for breath (πνεῦμα pneuma).
http://en.wikipedia.org/wiki/Neume
The Guidonian hand was known in Ireland at the close of the eleventh century
http://en.wikipedia.org/wiki/Guidonian_hand
The pre-Christian Irish had their ogham music-tablature, and the Irish of the seventh-eleventh century had the neumal accents, after which the Guidonian system was adopted The Guidonian hand was known in Ireland at the close of the eleventh century
Ogham = An ancient British and Irish alphabet, consisting of twenty characters formed by parallel strokes on either side of or across a continuous line. The very word ogham suggests at once a musical signification, and, therefore, it is of the very highest importance to claim for Ireland the earliest form of musical tablature.
http://www.claddaghdesign.com/blog/history/a-guide-to-the-ogham-alphabet/
A neume (/ˈnjuːm/; spelled neum in, for instance, the Solesmes publications in English)[1][2][3] is the basic element of Western and Eastern systems of musical notation prior to the invention of five-line staff notation. The word is a Middle English corruption of the Greek word for breath (πνεῦμα pneuma).
http://en.wikipedia.org/wiki/Neume
The Guidonian hand was known in Ireland at the close of the eleventh century
http://en.wikipedia.org/wiki/Guidonian_hand