Charles H. Spurgeon on Psalms 81:2

The Psaltery. It is probably impossible to be sure as to what is intended by a psaltery. The Genevan version translates it viol, and the ancient viol was a six stringed guitar. In the Prayer book version, the Hebrew word is rendered lute, which instrument resembled the guitar, but was superior in tone. The Greek word "psalterion" denotes a stringed instrument played with the fingers. Cassidorus says that the psaltery was triangular in shape, and that it was played with a bow. Aben Ezra evidently considered it to be a kind of pipe, but the mass of authorities make it a stringed instrument. It was long in use, for we read of it in David's time as made of fir wood (2Sa 6:55), and in Solomon's reign, of algum trees (2Ch 9:11), and it was still in use in the days of Nebuchadnezzar.