Calvin believed the use of instruments to be one of the elements of worship that was abrogated in Christ. On Ex. 15:20 (Miriam taking up her tambourine), Calvin writes, “…musical instruments were among the legal ceremonies which Christ at His coming abolished; and therefore we, under the Gospel, must maintain a greater simplicity.”
Elsewhere he writes, “In a word, the musical instruments were in the same class as sacrifices, candelabra, lamps and similar things. Those who take this approach are reverting to a sort of Jewishness, as if they wanted to mingle the Law and the Gospel, and thus bury our Lord Jesus Christ.”
It seems to me Calvin thinks the use instruments is both a return to the shadows and a return to infancy or immaturity. But the throne room of God has within it…and the people of the New Heavens and New Earth use…instruments.
There may have been good pastoral reasons to move away from instruments when reforming the worship and worshippers of Geneva. The more their service of worship smacked of Roman practices, the more the people would remain in bondage to their idols. So, I get why he and Luther despised the organ; and get why they would go further than dismantling their organs.
But Scripture does not obligate us to refrain from using instruments in worship…