Verses with the word organ in the Old Testament (3 verses):

Genesis 4:21
And his brother's name was Jubal: he was the father of all such as handle the harp and organ.

Job 21:12
They take the timbrel and harp, and rejoice at the sound of the organ.

Job 30:31
My harp also is turned to mourning, and my organ into the voice of them that weep.