A new theory has emerged to propose a psychological paradigm which explains the psychological effects of music.

Daniela and Bernd Willimek are the authors of an interesting 86-page booklet on this. It can be consulted online by clicking on this link:

http://www.eunomios.org/

Then, click on the Index of Contributions (top left side of the page), and when the index opens, look for the name of the authors, and you'll have access to a PDF copy of the book.

Bernd Willimek holds a graduate degree in music and composition from Karlsruhe University of Music in Germany, where his wife Daniela Willimek is a lecturer (she majored from the same university in piano performance). Bernd is the creator of the theory.

Here is an excerpt of the introduction:

The Theory of Musical Equilibration (known in the original German as the Strebetendenz -Theorie) is the first to create a psychological paradigm which explains the emotional effects of music. It breaks down musical sequences into one of their most essential components ― harmony ― and directly uses this material as the basis of its argumentation.

Harmony is essentially music in its concentrated form, since within a single moment it can reflect melodic and other musical processes which otherwise can only be depicted over a given interval of time. The psychology of harmony is the psychology of musical feelings. This book uses selected examples from the repertoire to make clear that the emotional character of musical harmonies cannot only be systematically deconstructed, but plausibly justified and empirically demonstrated.
Further down, we get a better glimpse of what it is about:

To a certain extent, the basic assertion of the Theory of Musical Equilibration is a revised interpretation of what Ernst Kurth described upon listening to music: the perception of forces at work . Willimek's original German term is "Strebetendenz," literally the "tendency to strive." It is an inherent desire for musical resolution, a driving force that
anticipates musical equilibration. Ernst Kurth spoke of perceiving the musical notes' desire to resolve, whereas the Theory of Musical Equilibration states that this phenomenon is the listener identifying with a desire for there not to be any musical resolution ― for things to remain the same. When Kurth speaks of a change in pitch in a major chord that
strives to resolve into a third, the Theory of Musical Equilibration explains this phenomenon as the consequence of the listener wanting things to stay as they are: the listener identifies with a desire for the third not to change in pitch.

Another key element of the Theory involves the emotional act Ernst Kurth observed when he wrote of internally translating the physically perceived tone into another essential quality. This quality can best be described as something
indefinably substantial. We do not experience a musical note as a frequency, but as an indefinable thing, albeit one
which we cannot logically attribute to part of our material world. However, it is this very inability to integrate a note into the material world that is the key factor which allows us to experience music on an emotional level. Listeners experience a sense of desire which revolves around something indefinable but substantial , something which is a pure and nearly undefined will that opens up endless opportunities in their imagination.
The authors then proceed to demonstrate in detail the above effects, including, with musical examples.

It's an interesting read.

The authors have a Twitter feed where they post comments on this theory. Search for "musical equilibration" on Twitter to learn more.