Very sorry to hear this. A great singer, whom we never quite heard enough of.
Archie Fisher wrote a poem for him, which was quoted on the back of his first LP sleeve :

"The Ballad Singer"

I watched a piper take the wind that blew around his hair,
And with the supple leather lead
The hard black wood and brittle reed
A dance into the air.

I watched a boy that stood with men
A whistle at his tongue
Breathe the old and smokey air into his breast,
Then with his careful fingers,
Make it young.

I saw a chin rest on a fiddle
And watched the fingers dance
Letting the notes slip from the strings
Into the wind that takes all things,
That music leaves to chance.

I heard the singer read the wind
And listened to his song,
That told of all the wind had known
And when and where the wind had blown,
And why he'd been so long.

To Al O'Donnell, 1968, by Archie Fisher

R.I.P., Al.