The study of counterpoint is part of any well-rounded musician's training.  From a historical and interpretive standpoint it is useful to understand polyphonic composition.  The most influential styles are the modal species counterpoint of the 16th century as exemplified by Palestrina, and the tonal counterpoint of the 18th century exemplified by J. S. Bach. The basic voice leading prinicples of the 18th century style form the basis of much modern and popular music and are particularly valuable for arrangers.