"When To Her Lute Corinna Sings"
by Thomas Campion

When to her lute Corrina sings,
Her voice revives the leaden stringes,
And doth in highest notes appear,
As any challeng'd echo clear;
But when she doth of mourning speak,
Ev'n with her sighes the strings do break.

And as her lute doth live or die,
Led by her passion, so must I,
For when of pleasure she doth sing,
My thoughts enjoy a sudden spring,
But if she doth of sorrow speak,
Ev'n from my heart the strings do break.

Notice the balance between the two stanzas of the poem.  For the most part, the lines in the first stanza balance the lines in the second one.

The lute is somewhat like an early banjo or guitar.  When Corinna is happy, the lute does well; when she sings an unhappy song, the strings break.  Then the poem compares the state of the lute to the state of the poet.  We can also see an implied comparison between the lute and the poet's heart, a common enough image.  We still speak about the heart strings breaking.  The second stanza makes this comparison explicit.