The Composer or Conductor makes a grinding noise when it is turned on or when the arm starts moving down.
Solution:
Make sure the correct power supply is plugged in. If the 30v power supply for a Signature printer is plugged into the Composer it will cause a grinding noise as soon as it is plugged in or when the arm starts moving down.
The Composer or Conductor use a 24v power supply. See this article for complete specs.