I attended church of Christ most of my life (the last couple of years I have not felt comfortable with any organized religion) so maybe I can answer some questions. The wiki article odenata referenced seems to be fairly accurate as to their beliefs and teachings in general, at least by my understanding of things

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The churches are not organized into any centralized group, every congregation is supposed to be autonomous. The congregation I attended as a child did not use "disfellowship" very often- I can only think of twice in the 18 years I attended before I left for college (and never in the congregations I attended as an adult for 16 years or so). Usually it was for someone in the congregation who was "flagrantly continuing in sin" despite all attempts by the elders to show that person they they were wrong. We heard of other congregations that would use disfellowship if they had a disagreement with another congregation about interpretation of something in the Bible, or to show that they were separate from "unbelievers" and say non-members were disfellowshipped, but the elders and most of the members of my congregation believed the Bible did not mean that.
The music issue is also as odenata states- because the whole intention of the church of Christ was to be as the church was in the first century, they didn't use instruments, so we didn't either. Growing up I heard the verse "sing and make music in your heart to the LORD" as an inference that God did not want instrumental music used in worship to Him. However, there are a very small number of churches that are instrumental and still are church of Christ- since there is no central organization, there are differences with every congregation. All of the congregations I have attended were a capella churches, but none of them taught that instruments were evil or anything, just not what God wanted.