Fintan Vallely (ed)
The Companion to Irish Traditional Music
Cork University Press, 1999
This book is not only an excellent encyclopedia of Irish music past and present, with a wealth of background information, it also contains a substantial entry under "harp" with contributions from Gráinne Yeats and Ann Heymann.
This book is available by special order only. If you would like me to get a copy for you please contact me.