(145) This makes it possible to collect in a convenient form two contrasting and valuable records, one preserving such effects of color as are generally called pleasing, and another of such groups as are found unpleasant to the eye. Out of such material something may be gained, more reliable than the shifting, personal, and contradictory statements about color harmony now prevalent. CHAPTER VII. COLOR HARMONY. +Colors may be grouped to please or to give annoyance.+ (146) Attempts to define the laws of harmonious color have not attained marked success, and the cause is not far to seek. The very sensations underlying these effects of concord or of discord are themselves undefined. The misleading formula of my student days--that three parts of yellow, five parts of red, and eight parts of blue would combine harmoniously--was unable to define the _kind_ of red, yellow, and blue intended; that is, the hue, value, and chroma of each of these colors was unknown, and the formula meant a different thing to each person who tried to use it. (147) It is true that a certain red, green, and blue can be united in such proportions on Maxwell discs as to balance in a neutral gray; but the slightest change in either the hue, value, or chroma, of any one of them, upsets the balance. A new proportion is then needed to regain the neutral mixture. This has already been shown in the discussion of triple balance (paragraph 82). (148) Harmony of color has been still further complicated by the use of terms that belong to musical harmony. Now music is a _measured art_, and has found a set of intervals which are defined scientifically. The two arts have many points of similarity; and the impulses of sound waves on the ear, like those of light waves on the eye, are measured vibrations. But they are far apart in their scales, and differ so much in important particulars that no practical relationship can be set up. The intervals of color sensation require fit names and measures, ere their infinite variety can be organized into a fixed system. (149) Any effort to compare certain sounds to certain colors soon leads to the wildest vagaries. +Harmony of sound is unlike harmony of color.+ (150) The poverty of color language tempts to a borrowing from the richer terminology of music. Musical terms, such as “pitch, key, note, tone, chord, modulation, nocturne, and symphony,” are frequently used in the description of color, serving by association to convey certain vague ideas.