Wynkyn de Worde, in "The Golden Legend":--

"Soon after, as God would, they saw a fair island, full of flowers,
herbs, and trees, whereof they thanked God of his good grace; and anon
they went on land, and when they had gone long in this, they found a full
fayre well, and thereby stood a fair tree full of boughs, and on every
bough sat a fayre bird, and they sat so thick on the tree that uneath
[scarcely] any leaf of the tree might be seen. The number of them was so
great, and they sang so merrilie, that it was an heavenlie noise to hear.
Whereupon St. Brandan kneeled down on his knees and wept for joy, and made
his praise devoutlie to our Lord God, to know what these birds meant. And
then anon one of the birds flew from the tree to St. Brandan, and he with
the flickering of his wings made a full merrie noise like a fiddle, that
him seemed he never heard so joyful a melodie. And then St. Brandan
commanded the foule to tell him the cause why they sat so thick on the
tree and sang so merrilie. And then the foule said, some time we were
angels in heaven, but when our master, Lucifer, fell down into hell for
his high pride, and we fell with him for our offences, some higher and
some lower, after the quality of the trespasse. And because our trespasse
is so little, therefore our Lord hath sent us here, out of all paine, in
full great joy and mirthe, after his pleasing, here to serve him on this
tree in the best manner we can. The Sundaie is a daie of rest from all
worldly occupation, and therefore that day all we be made as white as any
snow, for to praise our Lorde in the best wise we may. And then all the
birds began to sing evensong so merrilie that it was an heavenlie noise to
hear; and after supper St. Brandan and his fellows went to bed and slept
well. And in the morn they arose by times, and then those foules began
mattyns, prime, and hours, and all such service as Christian men used to
sing; and St. Brandan, with his fellows, abode there seven weeks, until
Trinity Sunday was passed."