'mental formula' of the subject; (b) functional substitutions; (c) phenomena of induction; (d) commisural disturbances. §2. General nature of musical aphasia, or amusia. Music is a language of the emotions; massive, not concrete, as is articulate language. The analogy does not go far: word and tone have very different language-values. On the other hand, the processes of acquisition and education are parallel in the cases of speech and music; whence it is intelligible that similar disturbances should arise in them. Yet a systematic treatment of amusia was not attempted until quite recently (Ballet, 1888; Knoblauch, 1890; Wallaschek, 1891). §3. Physiology of mental representations of music. (a) Part played by auditory images in music. — These are the most important mental images. The development of the centres is very different in different cases: auditory daltonism occurs. Hence Ballet's view, that musical deafness cannot precede word deafness (cf. Ribot's law of memory), is untenable. Auditory images may take the quality of a voice, of a familiar instrument, or of an indefinite, mean instrument. They may be externalized (hallucination). In the representation of harmonic chords a visual image may supplement the auditory. Of 60 musicians, 51 were pure 'auditifs'; 9 stated that they also employed visual or motor images. The figures have no absolute value. (b) Part played by motor images in music. — The motor images (Stricker) fall into three classes. α. Song. — Physiology, like pathology (Ballet's motor amusia; cf. Broca's aphasia, = aphemia) points to the existence of a motor centre of musical memory. The muscular synergies, which singing has set in activity, leave us a residual image in this centre. β. Instrumental performance. — There are also motor centres for the playing of instruments; cf. the 'finger-memory' of musicians. Pathology speaks for their existence (Charcot). γ. Rhythm. — Music was originally the accompaniment of muscular movements, which physiological necessity renders rhythmical. The motor rhythm-image is distinct; it may be left intact, when the song-image is pathologically changed (Wallaschek's paramusia) . (c) Part played by visual images in music. The visual images may be very precise; usually they are approximate or schematic only. 4. Pathological cases: musical amnesia (amusia). (a) Mixed or total musical amnesia (complex amnesia). — Here we have simultaneous functional failure of all the centres for the registering and producing of images. Two cases are cited, and further investigation demanded. (b) Special musical amnesia (simple amusia) . α. Auditory amusia or tone-deafness (Wallaschek, Grant Allen). — One case is cited. In ideal tone-deafness the subject, aphasic or not, hears a melody as a series of noises, without significance or aesthetic association. His memory for melody ceases. He may read music still, but without appreciation. Song is impossible. β. Visual amusia or notal blindness.
