Here in this older work he has attempted to examine everything he can possibly find about the musical practices of the first century New Testament church. He leaves no stone unturned as he delves into New Testament evidence, secular evidence, and historical evidence before even considering doctrinal ramifications. He even does his best to find "Statements Favorable to Instruments" and can only find a very few, all of which deal with non-religious private functions.
He spends a good deal of time quoting the writers of the period who, when even mentioning instruments, by and large use them in figurative ways such as, "The psalterion is the pure mind moved by spiritual knowledge. The kithara is the practical soul moved by the commandments of Christ" (Origen of Alexandria). Quotes like that are plenteous. He also mentions that the Greek Orthodox Christians, who divided from the Roman Catholic Church and certainly knew the Greek language better than any of us, objected to instrumental music accompanying the worship and still sing a capella. (As an aside, they also know the Greek word baptizo and will not practice sprinkling for the same reason.) The very term a capella means "in the style of the church," an open confession to the fact that everyone knew you did not have musical instruments in Christian worship.
Another factor he discusses is the very nature of the worship in the church. While Jewish worship in the Temple was all about ritual and physical show, the church became the spiritual Temple and its worship a spiritual worship. Once synagogues began, even Judaism did away with the instruments. Their worship had become centered on the Word of God rather than spectacle and they felt it no longer had a place. Interesting, to say the least.
A final section on doctrine should leave you convinced. If nothing else matters, a capella singing will not lead to division while forcing an instrument into the worship will send those who feel they can no longer worship acceptably out the door.
I found this book listed by more than one publisher. It is available on Amazon, Abebooks, Thriftbooks, and Ebay, and probably others. Be sure you get the one by Everett Ferguson.
Dene Ward