If we apply this classification to music we see at once that improvising comes under the second head: improvising is thinking or composing while playing. But the greatest musical ideas are those which are conceived entirely in the mind, which needs no pen or piano mechanically to stimulate its creative power. Of this there can be no question, whatever. With an almost absolute unanimity we find that the greatest composers conceived their immortal ideas in the open air, where there was no possibility of coaxing them out of an instrument. And not only is the bare outline thus composed mentally, but the whole composition with all its involved harmonies and varied orchestral colors is present in the composer's mind before he puts it down on paper. The composition of "Der Freischuetz" affords a remarkable confirmation of this statement. Weber began to compose this opera mentally on February 23, but did not write down a single note before the second of July. That is, he kept the full score of this wonderful work in his brain for more than four months, and, as his son remarks, "there is not a number in it which he did not work over ten times in his mind, until it sounded satisfactory and he could say to himself 'That's it,' and then he wrote it down rapidly without hesitation and almost without altering a note." This power of elaborating a musical score in the mind, and hearing it inwardly, is a gift which unmusical people find it difficult to comprehend, and which even puzzles many musical people. Yet it is a power which all students of music ought to possess; and, like other capacities, it can be easily cultivated and strengthened. A comparison with two other senses will throw some light on the matter. Most of us can, by thinking fixedly of some appetizing dish, recall its flavor sufficiently to start a nerve current and stimulate the salivary glands. The image of the flavor, so to speak, makes the mouth water. What do we do when we go to a restaurant and look over the bill of fare? We simply, on reading the list, recall a faint gastronomic image, as it were, of each dish, and the one which is most vivid, owing to the peculiar direction of the appetite, decides our choice. The sense of sight presents many curious analogies. Mr. Galton, in his "Inquiries into Human Faculty," gives the results of a series of investigations which show that there are great differences among persons of distinction in various kinds of intellectual work in the power of recalling to the mind's eye clear and distinct images of what they have seen. Some, for instance, in thinking of the breakfast table, could see all the objects--knives, plates, dishes, etc., in the mental picture as bright as in the actual scene, and in the appropriate colors; others could recall only very dim or blurred images of the scene, or none at all; and all stages, from the highest to the lowest visualizing power, were represented in the letters he received on the subject.