I currently have all axes set to 1/8 micro stepping. I have AM882 drivers and Nema23 4.2A 3.2mh from CNC4YOU. In Mach3 I've got Velocity on 2500mm/min and acceleration set to 800mm/s/s on all axes.

It's weird because when the Z axis moves slowly (for example, approaching the surface for cutting), it doesn't make that sound. It seems like sometimes Mach3 is able to control the steppers at low speed without having them sing, while at other times they sing like a choir.

Reducing the MCS would lower accuracy right ?