There have been many notable descriptions of music but perhaps one of the most apt from the viewpoint of law and commerce was Ian Hay's statement, "Music is about the most vulnerable piece of property that a man can bring into the world, especially today. " With the increased use of music brought about by technological advances, such as radio, sound films and tele­ vision, and the concomitant decrease in the sale of sheet music and phonograph records, the need for writers and publishers of music to share in the revenue from public performances became urgent. With this urgency the author's rights in the public per­ formance of his music became the subject of much literature and litigation which continues to this day. The purpose of this book is to present a clear picture of this much written and litigated about subject: the au'thor's right in the public performance of his music. In order to do this we must indicate not only the nature of the right but also how it is exer­ cised for it should be evident that with performances taking place throughout the world and in a multitude of ways, the exercise of the right by an individual author or publisher would present insurmountable problems.