The Shakespearean Sonnet Sonnet

I come to sing the praises of a form
That tends to have five rising feet per line,
And fourteen lines. And rather more than warm
My feelings are; I find it, oh, so fine!
Now four-foot lines, though easily composed,
Produce a relatively sing-song sound;
Indeed, unless the poem is quickly closed,
Asleep is how its hearers may be found.
And often at line 9 one will discern
A turning point; and since, so far, of rhyme
I've nothing said, to that I'd like to turn,
And point out that up until this time
The rhyme has alternated. But no more:
A rhyming couplet really shuts the door!