My harp also is turned to mourning, and my organ into the voice of them that weep.

Jamieson-Fausset-Brown Bible Commentary

31. organ-rather, "pipe" (Job 21:12). "My joy is turned into the voice of weeping" (La 5:15). These instruments are properly appropriated to joy (Isa 30:29, 32), which makes their use now in sorrow the sadder by contrast.

Matthew Henry's Concise Commentary

30:15-31 Job complains a great deal. Harbouring hard thoughts of God was the sin which did, at this time, most easily beset Job. When inward temptations join with outward calamities, the soul is hurried as in a tempest, and is filled with confusion. But woe be to those who really have God for an enemy! Compared with the awful state of ungodly men, what are all outward, or even inward temporal afflictions? There is something with which Job comforts himself, yet it is but a little. He foresees that death will be the end of all his troubles. God's wrath might bring him to death; but his soul would be safe and happy in the world of spirits. If none pity us, yet our God, who corrects, pities us, even as a father pitieth his own children. And let us look more to the things of eternity: then the believer will cease from mourning, and joyfully praise redeeming love.