"Contemporary Christian artists almost always use instruments in their recordings and concerts. Their music is instrumentally conceived, and without instruments (in traditional a cappella settings) the music doesn't work effectively. Instrumentally accompanied church music provides the singers/congregation with harmonic and rhythmic backgrounds. In such an environment, there is much less need for singers to employ and appreciate harmony. Praise teams to a great extent exist to provide, promote and perpetuate harmony for the congregation. When churches embrace the contemporary sound, they are led to make accommodations — trained singers, sound systems, instrumental accompaniment, vocal and instrumental percussion, and the like. I find it interesting that among instrumental churches of various descriptions that I have visited, I don't hear much real singing by the congregation going on. I have thought on many occasions that if the electrical power were cut off, there would be very little sound of singing by the congregation. The congregation increasingly is playing the role of observer rather than participant."
Arthur Shearin is a director of concert choir and former music department chairman at Harding University in Searcy, Arkansas. Quoted in article "Take notes: Church music lacks true harmony, singing experts say" by Tamie Ross in The Christian Chronicle.