90 DIFFICULTY OF DIRECT ANALYSIS. [IV. § 46.
He may however altogether fail in performing the analysis with the unassisted ear. This by no means indicates any aural defect, as he may at first be inclined to imagine. It rather shows that the life-long habit of regarding the notes of individual sound-producing instruments as single tones cannot be unlearned all at once. The case is analogous to that of single vision with two eyes, where two distinct and different images are so blended together as to appear to all ordinary observation as one. The acoustical observer who is thus situated must rely on the analysis by resonance, and on the evidence of those who are able to perform the direct analysis. As he pursues the subject further experimentally, his analytical faculty will develope itself.
46. The composite character of musical sounds, which we have recognised in the case of the pianoforte, and shall have ample opportunity of verifying more generally in the sequel, requires the introduction here of certain verbal definitions and limitations. The phraseology hitherto employed, both in the science of Acoustics and in the theory of Music, goes on the supposition that the sounds of individual instruments are single tones, and therefore, of course, contains no term specially denoting compound sounds and their constituents. ' Sound,' ' note,' and * tone'