a festival or game. Etymologically, then, theory is an act of contemplation. It is observing and speculating upon as opposed to doing something.Aristides Quintilianus, who understood the concept in this way, constructed a plan of musical knowledge about ce 300 that may be outlined as follows:Although Aristides separated the purely theoretical from the practical, the entire field that he ordered is theoretical in a broad sense, the division under Theoretical being what might now be called precompositional theory, while the category Practical deals with compositional theory and the theory of performance. He was not so much dividing music as what can be said about music, consequently musical knowledge and thought.Not much needs to be added to this outline to embrace all modern musical knowledge. Certain of the categories need to be broadened; for example, the arithmetical ought to include mathematics in general, communications theory and artificial intelligence; natural theory should include psychological and physiological as well as physical acoustics. Under Theoretical one would add history, aesthetics, psychology, anthropology and sociology of music. Among the Artificial categories, the harmonic as understood by Aristides applied to tonal relations in terms of successive pitches and would have to be extended to simultaneous relations. Another technical category that one would add is that of timbre, comprehending instrumentation, orchestration and electronic media. Similarly, under Practical, melodic would be complemented by harmonic, while poetic would, as in Aristides day, embrace both written and improvised composition. A modern version of Aristides plan might then look as follows:I. Theoretical A. Scientific: 1. mathematical, 2. physical, 3. psychological, 4. physiological, 5. anthropological, 6. sociological B. Technical: parameters: 1. pitch, 2. duration, 3. timbre C. Critical: 1. analytical, 2. aesthetic, 3. evaluative D. HistoricalII. Practical A. Creative: 1. written composition, 2. improvisational, 3. synthetic (tape, computer, etc.) B. Pedagogical: 1. melody, 2. harmony, 3. counterpoint, 4. orchestration etc. C. Executive: 1. instrumental, 2. vocal, 3. electronic or mechanical, 4. dramatic and choreographic D. Functional: 1. pedagogical (e.g. children's songs), 2. therapeutic, 3. political, 4. military, 5. recreationalThis entire field has sometimes been called Musikwissenschaft, the science of music, or musicology. Although it is all theoretical in the sense that its method is thoughtful observation, only a relatively small part of this scheme is acknowledged as the province of the modern working theorist, namely the TheoreticalTechnical (I.B), the TheoreticalCriticalAnalytical (I.C.1), the PracticalCreative (II.A) and the PracticalPedagogical (II.B) categories, which may be assumed under the catchwords theoretical, analytical, creative and practical. Yet many of the books from earlier times that are commonly referred to as theoretical treatises address themselves to the whole area represented by the above outline. In this survey it will be important, therefore, to keep in mind three things: the conception of the theoretical function prevailing at a particular time, the audience for which a treatise was written, and the philosophical or practical goals of the author.CLAUDE V. PALISCA A Teoria e agora entendida como sendo principalmente o estudo da estrutura da musica. Esta pode ser dividida em melodia, ritmo, contraponto, harmonia e forma, mas estes elementos sao dificeis de distinguir