Analysis of When Nighttime Sings A Villanelle

I sing the gentle villanelle,
A villenesque so slightly said,
Howbeit the nighttide casts her spell.

And now the rune I know so well
Remains, remembered, in my head;
I sing the gentle villanelle.

As evening leaves and shadows dwell
The golden brightness all but fled,
Howbeit the nighttide casts her spell.

The flowing verse, her tale to tell,
Inhibitions adrift and shed,
I sing the gentle villanelle.

And owls resound about the fell,
The day replaced with night's instead,
Howbeit the nighttide casts her spell.

Yet me, contented, in my shell
Warmly, snugged and safe a-bed;
I sing the gentle villanelle
Howbeit the nighttide casts her spell.