If a unit of troops has a Musician in its front rank then an inspiring horn blast or rousing drum beat can turn retreat into a stalwart defence.
A fleeing unit with a Musician will gain a +1 Leadership bonus in any attempt to rally (note that a unit's Leadership cannot be increased to more than 10 in this way). Also, if close combat is drawn but one side has a Musician and the other doesn't, the side with a Musician wins the combat by one point. If both sides have a Musician then the result is still a draw.