There's not a string attuned to mirth

But has its chord in melancholy.

Thomas Hood (1798-1845): Ode to Melancholy.

Here the heart

May give a useful lesson to the head,

And Learning wiser grow without his books.

William Cowper (1731-1800): The Task. Book vi. Winter Walk at Noon. Line 85.

Love took up the harp of Life, and smote on all the chords with might;

Smote the chord of Self, that, trembling, pass'd in music out of sight.

Alfred Tennyson (1809-1892): Locksley Hall. Line 33.