I've seen several conversations that touch on this but don't recall seeing a satisfying answer to this. Presuming the old Reformed view that instruments are weak and beggarly elements of OT worship, it is said they once being OT elements of worship cannot have a circumstantial NT use in worship. Is that just in worship that this rule applies; how do they have any use at any time if some past elemental use makes them illicit for a circumstantial of one kind, in worship? The sacrifices, priesthood, etc. had no use outside OT worship, but musical instruments were used so and in other cultures and are so used now. While an elemental use has passed with the ceremonies, can musical instruments serve a circumstantial use now in any way to aid the singing? Can someone play a few bars on an instrument instead of singing or humming or using a pitch pipe to remind of the tune before the congregation sings? Can someone play unobtrusively along to aid the singing? If so, where is the line between acceptable and unacceptable use? Where in Scripture is a rule that something that had an elemental function in the OT can never have a circumstantial use in the NT?