Instruments in worship

According to The Jewish Encyclopedia, instrumental music in divine services ceased with the destruction of the Temple. Music was generally prohibited as a token of mourning for the destruction of Jerusalem, except on festal occasions and especially at marriage ceremonies, to delight and make happy the bridegroom and bride.

The Jewish Encyclopedia (article signed 'A. J. D. E.'), The Jewish Encyclopedia (New York: Funk & Wagnalls, 1901-1906), vol. 9, s.v. 'Organ' — Article 'Organ', section 'Cessation of Instrumental Music'

Clement says the one instrument of peace, the Word alone by which we honor God, is what we employ. He says we no longer employ the ancient psaltery, trumpet, timbrel, and flute, which those expert in war and despisers of the fear of God used in their festive choruses to lift dejected minds.

Clement of Alexandria, The Instructor (Paedagogus), Book II — Ante-Nicene Fathers, vol. 2 (ed. Roberts-Donaldson, rev. Coxe) — The Instructor, Book II, Chapter IV, 'How to Conduct Ourselves at Feasts'

Aquinas says teaching should not be accompanied by artificial instruments such as the flute or harp, since they move the soul to pleasure rather than create a good disposition. He explains that the Old Testament employed such instruments because the people were coarse and carnal, needing arousal, and because these material instruments were figures of something else.

Thomas Aquinas, The Summa Theologiæ of St. Thomas Aquinas, Second and Revised Edition, 1920; literally translated by Fathers of the English Dominican Province — Secunda Secundae, Question 91, Article 2 ('Whether God should be praised with song?'), Reply to Objection 4

Chrysostom says David formerly sang psalms, and we sing with him today. David had a lyre with lifeless strings, but the Church has a lyre with living strings: our tongues, which have a different tone yet a more accordant piety.

John Chrysostom, as quoted by Edward Dickinson, Music in the History of the Western Church (Edward Dickinson; Project Gutenberg eBook #43208) — Chapter II, 'Ritual and Song in the Early Christian Church' (Dickinson quoting St. Chrysostom)

Calvin says the Levites were justified in using instrumental music under the law, because God willed to train his people as children by such rudiments until Christ. Now that the gospel’s clear light has dissipated the law’s shadows and taught a simpler service, imitating what the prophet enjoined only for his own time would be foolish and mistaken.

John Calvin, Commentary on the Book of Psalms, Volume 3 (translated by James Anderson) — Commentary on Psalm 81, in the comment block on vv. 1-3 (paragraph beginning 'With respect to the tabret, harp, and psaltery')

Albert Barnes says the prevailing character of music in the worship of God should be vocal. If instruments are used, they should be subordinate so that the service is characterized as singing.

Albert Barnes, Albert Barnes' Bible Commentary (Notes on the New Testament) — Comment on Ephesians 5:19 (the entry on 'Singing')