Interpreting Campion

I'm a dunce when it comes to interpreting poetry, and even more of a dunce when it comes to interpreting older poetry.

We'll be singing "Tune Thy Music To Thy Heart" tomorrow (to a tricky-ish composition by Alec Rowley), and still, the phrase "and so thy sorrow" is giving me trouble, linguistically. I more or less get it, but I don't get it enough to explain it to others. Would any of you be able and kind enough to explain it to me, the English poetry lay(wo)man?


Tune thy Musicke to thy hart,
Sing thy joy with thankes, and so thy sorrow:
Though Devotion needes not Art,
Sometimes of the poore the rich may borrow.

Strive not yet for curious wayes:
Concord pleaseth more, the lesse 'tis strained;
Zeale affects not outward prayse,
Onely strives to show a love unfained.

Love can wondrous things affect,
Sweetest Sacrifice, all wrath appeasing;
Love the highest doth respect;
Love alone to Him is ever pleasing.

Today's Horoscope:

Gemini: Your mental gears are fully engaged right now, and you can work through even the toughest problems. It's one of those days when you might feel a bit cold-hearted, but you know you're doing what's right.