Normal churches have choirs. Soprano, alto, tenor, bass. Four voices create harmony. The Amish — everyone sings one melody. In unison.
Why
Harmony singles out voices. Someone has beautiful soprano — everyone watches. Someone has powerful bass — everyone admires. That's Hochmut. In unison, all are equal. No 'good' voice or 'bad.' One voice of the community.
Sound
200 people singing one note. Not boring — powerful. Like an organ, but living. Walls of the wooden house vibrate. Children feel the sound on their skin. Not music — a physical experience.