Faith & Reason Nexus

• J. N. BROWN, The Encyclopedia of Religious Knowledge, p. 852
  “That instrumental music was not practiced by primitive Christians, but was an aid to devotion of later times, is evident from church history. The organ was first introduced into the church by Marianus Sanatus in the year 920; and the first that we know in the West was one sent to Pepin by Constantine Copromymus about the middle of the eighth century.”
• J. N. BROWN, The Shaff-Herzog Encyclopedia of Religious Knowledge, Vol. II, p. 1702
  “In the Greek church, the organ never came into use, but after the eighth century, it became common in the Latin church, not however without opposition from the side of the Monks… The reformed church discarded it, and though the church of the basis very early introduced it, it was in other places admitted only sparingly and after long hesitation.”

Summary:

These quotes highlight the historical development of instrumental music in Christian worship. Initially, early Christian practices did not include instruments in worship, and the use of the organ was introduced later in church history, specifically in the Latin Church around the 8th century. However, the Greek Church never adopted it, and some forms of Christian tradition, including the Reformed Church, opposed or hesitated to accept the use of instrumental music in worship.