I have just read Sean-nos & Scots Gaelic Psalms which I found very interesting. I believe the sharp tone quality of the singer she was referring to(probably Brigette Fitzgarald)is the nasal quality characteristic of sean-nós. Authorities on sean-nós will deny any tradition of group singing or harmony in the west of Ireland. It is unclear if this is because of tradition or ideas of Gaelic Revivalists. Sean-nós is actually a Gaelic Revival expression. John Moulden will probabably affirm that traditional singers in the North sing in unison. Any harmony would be the result of differences in individual style, not any attempt at formal harmony. Look for recordings of any combination of Len Graham, Robin Morton or Cathal Mc connell.

Brían.