He has not confined his work to the refinement of the merely mechanical parts, such as the instrument and the records, but during the last ten years he has devoted an immense amount of time to music itself. Becoming convinced that the public desired really beautiful music, he set himself to a thorough study of the subject, not only of compositions, but also of the human voice, its powers and limitations, and of different effects of various styles of orchestration. He determined to hear for himself music of all kinds, and with this object in view hired a number of sight-reading players and singers to render musical selections by the hour. [Illustration: "THE INSOMNIA SQUAD"--Copyright by Thomas A. Edison] In the past ten years he has heard upward of twenty-five thousand compositions of a wide range, from grand opera to ragtime. As he hears them he indicates his opinions, which range from "beautiful" to "punk," according to his idea of availability for the phonograph. An elaborate card system preserves these indications for further application in selecting music for the phonograph. It might seem dogmatic to have the reproduction of musical compositions depend upon his opinion, but it must be said that he is not entirely committed to such drastic measures if there is a real demand for some musical selection which does not seem to merit his good opinion. His decision as to a composition is not based on a merely personal whim or fad, but upon his opinion of it from the standpoint of an inventor. He has said to the writer more than once: "There is invention in music just as much as in the arts. Composers such as Verdi, Rossini, Bellini, Donizetti were inventors. They did not copy, nor did some of the other great composers. But the rank and file of musicians are not inventors; they have copied the ideas of the others, consciously or unconsciously. If you will sit down for a few hours and have a lot of miscellaneous compositions played you will be convinced of it." Edison has had no musical training, as the term is generally understood, and the writer must confess that before hearing the above expression he failed to comprehend the true basis of the inventor's opinions of the various compositions played or sung for him. On several occasions he therefore arranged (unknown to Edison) to have one or more compositions played or sung again after a lapse of some weeks, to see whether or not there would be any similarity of opinion to that first indicated. In every case Edison's judgment was practically, and in some cases precisely, the same as before, thus proving that the opinion first given was not merely a whim, but was based upon some definite line of thought in the inventor's brain.