Shakespearean sonnet cycle

Let me not to the marriage of true minds 
Admit impediments. Love is not love 
Which alters when it alteration finds, 
Or bends with the remover to remove: 
O no! it is an ever-fixed mark 
That looks on tempests and is never shaken; 
It is the star to every wandering bark, 
Whose worth's unknown, although his height be taken. 
Love's not Time's fool, though rosy lips and cheeks 
Within his bending sickle's compass come: 
Love alters not with his brief hours and weeks, 
But bears it out even to the edge of doom. 
    If this be error and upon me proved, 
    I never writ, nor no man ever loved.

Music to hear, why hear'st thou music sadly?
Sweets with sweets war not, joy delights in joy.
Why lovest thou that which thou receivest not gladly,
Or else receivest with pleasure thine annoy?
If the true concord of well-tunèd sounds,
By unions married, do offend thine ear,
They do but sweetly chide thee, who confounds
In singleness the parts that thou shouldst bear.
Mark how one string, sweet husband to another,
Strikes each in each by mutual ordering,
Resembling sire and child and happy mother,
Who, all in one, one pleasing note do sing.
  Whose speechless song, being many, seeming one,
  Sings this to thee: "Thou single wilt prove none."