Possible Clues:

• Ancient church music
• Unaccompanied church music sung in unison — a ninth clap (anag)
• One in church works outside creating religious music
• Music popular when having tea in factory
• Church article's lamentation about liturgical music
• Proposal by church worker to introduce one form of sacred music
• Singing a little way into the factory
• A short distance inside the factory there's unison singing
• Music composed by undistinguished church worker
• It's unaccompanied in church