Merriam Webster: ensemble speaking by a group often using various voice combinations and contrasts to bring out the meaning or tonal beauty of a passage of poetry or prose.
For someone that stutters, speaking the same words in unison as another person or group can result in fluent speech.
The use of Altered Audio Feedback (AAF) or Delayed Audio Feedback (DAF) which echoes a speakers words back to them can emulate choral speaking and improve fluency.