Boyd Clarke and Ron Crossland are experts in leadership communication. Their book "The Leader's Voice" discusses how leaders can use three essential channels - factual, emotional, and symbolic - to effectively convey important messages to constituents. It provides examples of how leaders like Golda Meir, Gandhi, and Lincoln inspired people with their voices. Leaders must overcome assumptions that messages are understood, agreed with, or will prompt action. They must skillfully employ all three channels to motivate and engage followers.