Burke, that is wonderful! It gives a marvellous description of "keening", so that you can almost hear it. Thank you. It ia a great shame that the tradition has been lost.
One of the great Irish poems The Lament for Art O'Leary (trans. Frank O'Connor) ends with his widow addressing the women who are about to sing the caoine over his body:

Take my heatr's love'
Dark women of the Mill,
For the sharp rhymes ye shed
On the rider of the brown mare.

But cease your weeping now,
Women of the soft , wet eyes
Till Art O'Leary drink
Ere he go to the dark school-
Not to learn music or song
But to prop the earth and the stone.

The account given by Clarke(?) suggests that the keeners sang improvisedly within a strict metrical pattern, which brings us exactly back to where this started; the Lewis psalm singing. It sounds so exotic that observers reach for some far-fetched analogies, as in Clarke's account where keening is compared to ancient Hebraic singing.