"Sing and make music in your heart to the Lord" (Ephesians 5:19, NIV).
In the Churches of Christ, we have maintained an ancient tradition of singing worship music without instrumental accompaniment. In many congregations, the music has been outstanding by any standard.
I was aware that a few other churches share the same musical tradition. In an interesting article in this month's Christian Chronicle, Bobby Ross reports on a gathering of those groups at Pepperdine University for a symposium of sacred a cappella music. (See the article at http://www.christianchronicle.org/modules.php?name=News&file=article&sid=742). I was intrigued by the perspectives of Eastern Orthodox Churches, Mennonite Churches, Churches of Christ, and a few Presbyterian and Baptist Churches. I did not realize that such diverse theological traditions share a common musical tradition (although each may have distinctive styles within the a cappella tradition).
In recent years, Jenks Church (our former congregation), the Richland Hills Church of Christ in Fort Worth, the Quail Springs Church of Christ in Oklahoma City, Northwest Church in Seattle, and a few other Churches of Christ have added a worship service in which instrumental music is used. However, I believe that each congregation has maintained an a cappella service, too. As unity among the Churches of Christ and Christian Churches is being re-established, I would love to hear about a few Christian Churches adopting a cappella services in their line-up of worship service options, too. It is a good tradition, and it would be nice to share it with other Christians who are not accustomed to it. (To be honest, Amazing Grace should never be sung with instrumental accompaniment.)