I've got to be honest though and say that I'm not certain that asking questions about the interpretation of the silence of Scripture is very important. For example I've been thinking recently about how all of our valued rules for understanding and defining doctrine would not have allowed Jesus to do what he did and would not have allowed the entrance of gentiles into the church. The clear, spoken, and understood doctrine of God's people was that to have relationship with the Lord you had to work within or in connection to the Jewish system. Additionally, there's no room for God to die in the jewish system (let alone on a tree!) What changed all this was the action of God. When Gentiles were filled with the Spirit, the Jewish community had to begin asking different questions concerning their theology.
Anyway, I say all that to say that I think we'd be better off in our churches if we spent time trying to help them see and experience the work of God. Is silence in Scripture prohibitive or permissive? My understanding is that it's a moot point because the better question is "has God's Spirit confirmed or denied the direction you're moving". And while I realize this is a much harder question to answer, and while I realize that this brings up a whole new set of questions (how to you identify if the Spirit has confirmed something?), I think it's worth grappling with.

lex orandi lex credendi (The rule of prayer is the the belief). If its all about traditions and relationships then there will be big, huge problems to come. Likewise if it's about doctine, same thing, big problems to come.

In order to proceed, Firstly the CofC should first determine if the Regulative Principle is a biblical understanding of scripture. If so why? (I would personally say it is Biblical)

Secondly, if one agrees that the principle is Biblical, one must then figure out how to apply the regulative principle consistently (forget music as that is too hot a topic to be discussed objectively in the CofC). (Currently the CofC seems (from an outside perspective) to have a very inconsistent application of the Regulative Principle thus fueling the worship wars from within it's own ranks). Regardless, once one understands the principle and how to apply the principle consistently to less controversial issues then proceed to talk about how to apply these principles to music specifically.

Even if you end up still not agreeing on music at least both sides should understand the basis for the decision and most likely realize that the biblical theology has not been over turned only the application. This should allow for a grace based conclusion.

But one thing that can not be ignored in the conclusion of any application of principle in worship is what are likely to be the long term ramifications for the change in worship. In other words will this change in worship change doctrine long-term in an unintended way. Mark 7 shows how a change in practice effected the doctrine of the Jews in an unintended way, so much so that Jesus has to correct them.

So by introducing a cappella only how does that change doctrine? Likewise instruments or even 4 part harmony; how can adding these change doctrine long-term? Either can be significant. Then having assessed the ramifications (both good and bad) either live with the ramifications or mitigate the ramifications proceeding in grace. Likely you will have to do both.

Personally I think the bigger question is what is the purpose of Sunday Service in the first place? When that question is answered correctly the rest seems to fall in line. Is their a biblical order, liturgy, to church? I would argue there is supposed to be. But both Baptist and Churches of Christ have a "Free Church" tradition which says "no." A position I don't think is defensible. There is a biblical order to "services."

Specifically Churches of Christ while knowing it or not, have a puritan interpretation of the regulative principle of the Westminster Confession. The Regulative Principle stating that which God does not specifically condone is not allowed in worship. So I think the discussion about music is better talked about in that context. Are Churches giving up the Puritan interpretation of the Regulative Principle? If so then what are they replacing it with? Perhaps the older generations & younger generations could have a more constructive conversation and come to some understanding if they first sought to understand the theological context of the discussion instead of simply talking about particular genres of music.