History of music psychology
In the ancient times, Pythagoras (570-510 BCE) and his collaborators empirically investigated the relation of the lengths of consonantly vibrating strings. They found out that the quotient of two such lengths is given by a simple ratio of integers. Worth mentioning is also the Greek physician Herophilos (334 – 279 BCE) who tried to establish connections between the human pulse and music.
During the 17th and 18th century, mathematicians as, Descartes (1596 - 1650), Huygens (1629 - 1675) and Euler (1707 - 1783) rediscovered the work of Pythagoras and tried as well to found the perception of music on arithmetics.
In the 19th century, the emergence of empirism was important for the creation of a systematic musicology. Researchers believed that empirical work, logical conclusion and also speculation were important to build up new theories. Musical theories often had a strong normative character.
For example, Hermann von Helmholtz (1821 - 1894) tried to explain the sensation of consonance and dissonance by the physiology of the human ear. In 1863, his book Die Lehre von den Tonempfindungen als physiologische Grundlage fuer die Theorie der Musik described music by decomposing it into the single elements of sound, and then explained the influence of music on human perception.
Helmholtz clarifies that sound is nothing else than oscillations of the air, where the amplitude of the oscillation specifies the loudness of the sound, the frequency determines the pitch, and the form of the oscillation defines the tone. More complex sounds are created by the addition of several waves. This can also create periodic waves if the single frequencies are integer multiples of each other or differently said if the overtones of the same fundamental. Another phenomenon which might result from the addition of single oscillations is the beat. This is the interference between two sounds of slightly different frequencies and leads to periodic variations in volume whose rate is the difference between the two frequencies. According to Helmholtz, the function of the ear is to decompose the sound into its parts. He showed by hearing experiments that this is the way tones are perceived. The function of the ear is to decompose the different the sound into its parts. Helmholtz showed by hearing experiments that this is the way tones are perceived. One example for such an experiment is the an exercise at a piano. Helmholtz proposed to play a g' followed by a c. In this case one can hear the g' as a part of the c. c has a frequency of 130.813HZ whereas g' has a frequency of 783.991Hz, which is about six times the frequency of c. So they are overtones of the same fundamental. Therefore the ear works like a Fourier transformation. It filters the different frequencies out of a superposition of waves. While Helmholtz considers consonances and dissonances to origin from the physiology of the ear, he thinks differently in the field of aesthetics. Helmholtz tries to find an explanation for our understanding of beauty of music. He is convinced that beauty is bound to laws and rules and hence human rationality. He sees the aesthetics of arts in the possibility to understand more and more the artwork contemplating it.
Another example is Hugo Riemann's (1849 -- 1919) attempt to build up a system of musical logic, which not only gave a normative theory of harmony but was also meant as a guidance for composing.
But there were also first cognitive attempts to musicology. A number of neurologists made observations about music abilities of aphasic patients. Neurologists started to describe cognitive processes involved in the perception and production of music by means of diagrammatic models. These diagrams were constructed by "centers" and "pathways". The "centers" represented areas in the brain where memories (e.g. memories of coordinate movements to produce music) are stored. The "pathways" are functional connections between centers. Observating a patient with motor aphasia (loss of the ability to produce and/or comprehend language), who could sing a song text although she was unable to neither recite nor verbalize the same words in speech, the German physician and anatomist August Knoblauch (1836 - 1919) developed in 1888 the first diagramatic model of music. In his model he differentiated between input and output processes and derived the existence of nine possible disorders of music production and perception. This model anticipated many ideas of the late twentieth century. 
At about 1930, a lot of knowledge was gathered together in systematic musicology. The most important methods which yielded this knowledge were introspection, phenomenological description and – last but not least – empirical work. One of the most important books from this time is “Tonpsychologie” by Carl Stumpf (1848 - 1936). Much of the musical research was done in psychological laboratories. For example, Carl Stumpf was in the first place a philosopher and psychologist. A lot of the empirical work of that time dealt with the perception of tone distances and intervals, of melodies, timbre and rhythm.
The close cooperation between psychologists and musicologists was one of the main ingredients of the arising of Gestalt psychology at - for example – Berlin, Leipzig, Vienna and Graz. (There are slightly different notions of Gestalt psychology, but all share the characterizing conviction that what happens to a part of an organized whole (a Gestalt) is determined by the immanent structure of this whole. A perfect example of such a Gestalt is a melody.) Gestalt research focused on on the perception of rhythm, pitch, melody, consonance, timbre, structural organization of musical space and other musical aspects.
With the rise of National Socialism in Germany, this cooperation ended almost abruptly when leading researchers in both fields emigrated.
After World War II, systematic musicology could not be established in its former form in Europe. There are mainly two reasons. The first reason is of course the emigration of many researchers. The second reason is a shift of scientific paradigm in the 1950ies in some branches of science: The arising fields of information theory and cybernetics had a great impact on many disciplines, including music psychology. In addition, the strongly behavioristic American psychology had a great impact on European thinking. Statistical testing became an obligatory method. These developments together with other methodological problems for testing its claims (for example the lack of brain scanning) made the Gestalt approach fall apart.
Other branches of research such as acoustics, physiology, sociology and aesthetics became more relevant for musicology. A result of these developments was that only a few researchers represented musicology as an own discipline, and they couldn't but follow the new developments. Many of them worked in the field of music sociology, regarding music as a social phenomenon rather then a phenomenon best understood in terms of perception and cognition. Musicology did not longer concern about pitches but about noises and environmental sounds in so called open structures.
Cognitive studies in psychology arised in the 1950/60ies, the publication of Ulrich Neisser's book “Cognitive psychology” in 1967 being a main event. From the 1970ies on, these led together with tools from information theory and engineering sciences to the emergence of so called cognitive musicology. First, cognitive musicology had a quite formal character being influenced by formal sciences such as mathematical logic and artificial intelligence. This led to the conception of the nature of musical representations which were conceived as symbols which were manipulated by rules. From the mid 1980ies on, issues of musical representations were considered and worked out in terms so called subsymbolic approaches based on neural networks and auditory models. In the 1990ies, both approaches (symbolic and subsymbolic) were also combined, and with the progress of computer technology, models of cognitive musicology are more and more computable. Another integral ingredient of cognitive musicology is the theory of semiotics, which was introduced to musicology in the 1970ies and mainly serves as a framework how to deal with music as an information.
Nevertheless, the Gestalt approach never completely disappeared and finds new interest in the last decades. For example in ethnomusicology, where new investigations on inherent patterns of certain African music give new evidence for the Gestalt approach. But also the cognitive approach in general provides new interest for a fundamental principle of Gestalt principle, the psychoneural isomorphism.
Of great historical interest is also the work of Curt Sachs (1881 – 1959) on the structure of medieval and primitive music. He shows that western civilization has misinterpreted the structure of this music for a long time - guided by prejudices, for examples that the church modes were an adequate framework for all medieval music. This was caused by the fact that in investigating medieval music, music historians for a long time only used information obtained from ecclesiastic sources. The rest of the article deals with Sachs' results on this issue. The main result on the structure of medieval music and also primitive music from many areas of the world is that this music is organized in chains of thirds.
Examples can also be found in Gregorian chant. In chains consisting of two thirds, a minor third is followed by a major third and vice versa. The vast majority of medieval melodies is structured in triple thirds. This discovery solves for example the problem that many melodies only fit vaguely the church modes (as for example recognized by Heinrich Besseler.) All triple-third melodies form two overlapping perfect fifths, resulting from the alternating minor and major thirds. Most such melodies have the chain structure DFAC, next in number is CEGB. But also quadruple chains are often found in secular and ecclesiastic medieval music as well as for example in (north American ) Indian music and in east African music.
Other examples of structural parallels in medieval music and primitive music such rhythmic structures or polyphony can be given.
Another evidence for this theory of chains of thirds is given by the system of music notation used today. It was introduced in the 11th century by Guido d'Arezzo (with four instead of five lines). This system has from today's point of view the drawback that two notes which differ by an octave are not both on a line or both in the space between two lines. But this system favors the notation of chains of thirds.
Finally, the seventh – important in triple-chains as well as in quadruple chains - yielded the octave. This development, as well as the development of harmony in Europe was favored by the fact that European music was and is mainly focused on instrumental music – not on singing. (Singing also takes place, but rather in singing of words or even poetry than in expressing emotions in vocal singing.) Now, instrumental music forces a more precise tuning than singing, and this in turn forces the developments just described.
- (For more information about the model by Knoblauch see the paper by Johnson, J.K. and Graziano, A.B., from which the content of this paragraph is taken.)