653 Your sovereign goddess' most dear delight, 654 Why do I send this rustic madrigal, 655 That may your tuneful ear unseason quite?

unseason > {Strike or affect disagreeably}

656 You only fit this argument to write,

You only > [Only you are] argument > subject-matter

657 In whose high thoughts Pleasure has built her bower,

bower > chamber, retreat

658 And dainty love learned sweetly to indite. 659 My rhymes I know unsavoury and sour

know > [know to be too]

660 To taste the streams, that like a golden shower 661 Flow from your fruitful head, of your love's praise, 662 Fitter perhaps to thunder martial stour,

stour > conflict, tumult