PIANO PLAYING MECHANISMS Being a Treatise on the Design and Construction of the Pneumatic Action of the Player-Piano and of the Reproducing Piano BY WILLIAM BRAID WHITE Associate of the American Society of Mechanical Engineers, Technical . Editor of the Music Trade Review, New York; Author of "Theory and Practice of Pianoforte Building," "Modem Piano Tuning," "The Piayer-Pianist," etc. WITH FIFTY-TWO ORIGINAL ILLUSTRATIONS AND A COMPLETE INDEX NEW YORK EDWARD LYMAN BILL, Incorporated 383 Madison Avenue Copyright, 1925, by EDWARD LYMAN BILL, Incorporated Entered at Stationers' Hall, London, England TO HIS FRIENDS IN THE PIANO AND PLAYER-PIANO INDUSTRIES Whose generous assistance has been indispensable to him in gathering materials for this book, THE AUTHOR GRATEFULLY DEDICATES THE COMPLETED RESULT PREFACE The object of this book is comprehended in its title. It represents an attempt to cover in a scientific manner and with sufficient completeness the present position of an art which has represented one of the most interesting and fascinating developments in the mechanical history of the Twentieth Century. The present work constitutes my third attempt to deal with the subject and is by all means the most complete. The fact is that the art has been developing at a remarkable rate of speed and in directions some of which were hardly foreseen when the last book left my pen. So vast indeed have been the changes since 1914 that when a new edition of my "Player-Piano Up To Date" seemed to be called for, I felt that it would be best to re-write the whole work from beginning to end, making it, with the many changes and additions, not a new edition of an old book but the first edition of a completely new one. I have to offer my heartfelt thanks to all the many friends within the player industry who have so kindly lent their aid in the gathering of materials without which this book could not have been writ- iii iv PREFACE ten. To name any one individual among so many would be to undertake an invidious task, so I have ventured instead to dedicate this work humbly and gratefully to them all. On the other hand, I must make specific and grateful mention of my brother, H. Sidney White, 0. E., who, at vast sacrifice of a busy man's time, undertook to make for me the exquisitely neat drawings which ornament this book, and form, perhaps, the greater part of its value, Only one who cared enough for the player-piano in itself and for its own fascination to engage in a seemingly endless and highly ungrateful labor for its sake would have taken upon himself the task of translating into mechanical clarity and precision the crude and hasty sketches from my pen, which have formed almost his sole guide from end to end. WILLIAM BRAID WHITE. Chicago, March, 1925. TABLE OF CONTENTS PAGE PREFACB ................................................................. iii CHAPTER I. First Principles .... 1 CHAPTER II. The Modern Player - Piano Described............................. 38 CHAPTER III. Dimensions and Pressures . 111 CHAPTER IV. Automatic Power and Auto- matic Expression . 129 CHAPTER V. The Reproducing Piano . 147 CHAPTER VI. The Coin - Operated Player - Piano .................................... 206 CHAPTER VII. Repair and Maintenance . 216 List of Illustrations . 233 Index......................................... 235 CHAPTER I. FIRST PRINCIPLES. The pieces of mechanism which are described in this book are known as "player actions," that term being an adaptation, or corruption, of the more comprehensive name, "piano-playing mechanism," meaning machines which, under the control of a music-sheet or "music- roll," operate the tone-producing elements of the piano and perform all kinds of music thereby. There are many varieties of these machines and their use is now so very general that everyone who undertakes the care of pianos must today be well acquainted with their nature and pe- culiarities, if he is not to find himself constantly in the presence of mechanical and musical difficulties which he is unable to solve. It is not to be expected that the readers of a book like this should be totally unacquainted with the piano itself. This musical instrument, of course, is the basic reason for the existence of the machines which are described in these pages, and, therefore, I should be justified in expecting from every reader a working knowledge at least of the piano action. For the sake of certainty, however, let me describe 1 2 Piano Playing Mechanisms in a few words the mechanics of tone-production of the piano. The description below is illustrated by Figure I. Mechanism of the Piano. Mechanism of the Piano. A steel string is stretched over a bridge made of wood which, in turn, rests upon a wooden "sound - board," or amplifying table. A "hammer," made of wood covered with felt, is mounted in front of this string and connected by means of what is called a movement or "action," with a "key" which can be depressed, or "struck," as we say, by the finger of the musician. When the key is thus depressed the hammer is moved forward until it is very nearly in contact with the string. Just before contact is established the mechanical connection between the hammer and the key is disengaged by a tripping device called an "escapement," so that the hammer is carried forward to its actual contact by the momentum of the motion first imparted to it when the key was depressed. The hammer thus strikes the string a percussive blow, exactly like the blow of a drum stick upon a drum head. The elasticity of the steel wire is sufficient to cause a reaction which throws the hammer back and away until it is caught by a part of the mechanism known as a "check," and is held there until the key has been released by the finger and is ready for another stroke. The piano, in fact, consists simply of eighty-eight 4 Piano Playing Mechanisms such separate string unisons, each with its mechanical movement as described. The illustration will show the points involved, and the reader should study it carefully. One meets so many men occupied with the production of piano playing mechanism who are imperfectly acquainted with the mechanical principles described above, that it seems proper to set these forth here in their very simplest form. It may be added that although the illustration shows the mechanism as applied to the vertical or upright piano, which is the form of most player-pianos, the principle remains the same in the horizontal or grand piano, although the mechanism of the latter is usually more elaborate and rapid in action. What the Player Does. Certain points must be noted before proceeding. The mechanical work of making a tone on the piano is extremely simple. It consists solely in causing the hammer to swing forward towards the string, with greater or less velocity, and to rebound before it can "block" the vibration of the latter. Obviously, therefore, the essential parts of the action consist of the hammer, the check and the escapement. Everything in FIG. 1 which is below the dotted line A.... B is incidental. The key is provided because the fingers of the musician cannot otherwise so well operate the hammer. If better arrangements could be made, they doubtless would by this time have appeared. That point must also be remembered. 5 First Principles Now the player action is nothing more than a set of appliances, one for each of the eighty-eight separate mechanisms which make up the piano action, intended to operate the hammers of the piano and so make tones as required. From what has been said above the reader will perceive that these appliances are required merely to cause the part of the piano action above the dotted line in FIG. 1 to turn on its various pivots and so cause the hammer to swing at the string. By making the simple experiment of putting one's finger under the "wippen" of the action (see FIG. 1) and lifting slightly, one can cause the wippen to swing on its pivot, followed by the other parts of the mechanism, causing the hammer to swing against the string. This shows that it makes no practical difference how or where the connection comes between the player action and the piano action, provided that the mechanical requirements described are fully complied with. Varying Hammer Velocity. Again, musical per- formance requires that tones be sounded with varying strengths. One tone must be loud, another soft, and so on. This, in turn, simply means that the musician must be able to vary the velocity of the hammer in its motion to the string. This he does by imparting greater or less velocity to the key with his finger. Various names and descriptions are given to the details of this process by musicians, but the essential facts are as stated. It is obvious that any mechanism which will impart to the wippen of 6 Piano Playing Mechanisms the piano action (see FIG. 1 again) a turning movement of which the velocity can be controlled, will enable the person who directly or indirectly controls that mechanism to simulate the tone variations produced on the keyboard of the piano by the musician. The musician varies his key velocity by his muscular action. The player action uses the pressure of atmospheric air. Let us briefly consider how this pressure may be utilized. The Sea of Air. We all know quite well that we live in a sort of sea of air, which surrounds us, penetrates within our bodies, is breathed in and out by us and extends to a great distance above our heads.