Modern musicology defines music as

a medium of communication that provides the possibility of creative expression for the individual in relation with his total pattern of behaviour.¹⁾

Expression belongs to the field of psychoacoustics. It is based on three levels:

1. Design (by the composer),
2. performance (by the artist) and
3. perception (by the listener).

The expressive performance of music is generally preferred. Mechanical performance is understood as its opposite. When performing, you should therefore aim

to reconcile the score with your own musical feelings and emotions, in tune with the instrument you play on and the space you are in, with the listeners who are present or missing, and with every other conceivable circumstances, by which every conscious reproduction, devoted to the moment, receives uniqueness, distinctiveness and thus beauty.²⁾

Across the various genres of music, e.g. when comparing Classical music with Jazz and pop music, „continuities“ can be shown in

the way in which dynamics, vibrato, portamento, vocal timbre, and ornamentation delinate musical structure and communicate a narrative or emotional intent.³⁾

Musical devices include:

Not all of them can be found in the score; often, their use is based on cultural conventions or decisions made by the performers.

Musical expressiveness depends on dynamic variation, accentuation, articulation, rhythmic alteration, tempo modification, and – in the case of vocalists, string and wind players – the variation of tone through use of vibrato and/or portamento. The extent to which such devices are applied (in other words, the quality and quantity) characterizes the hallmark of individual musicians.⁴⁾

Through these devices, musicians can move the listeners:

To a considerable extent we hear emotion in music because we hear motion and dynamic qualities in it. The „because“ here is most often cashed out in terms of a perceptible likeness between the movement and dynamic quality of music and the pace and posture of a person in a certain emotional state, e.g., a sad, happy, or angry one.⁵⁾

However, the exact contexts and modes of action of music have long been judged completely differently.

In the conception of Barock and Klassik, music represented a „language of sensation“;⁶⁾ Forkel even called it the „perfect language of the heart“:

Music, in its origin, as well as language, is nothing but sound-passionate expression of an emotion. They both spring from a common source, from sensation.⁷⁾

Music was to make clear and unambiguous messages to the listener about the emotional world of the composer, as Johann Mattheson demanded:

Since instrumental music is nothing but a tonal language or a speech of sound, it must always direct its real intention to a certain emotion, which to excite must be taken into proper account in the intervals, the clever division of movements, the measured progression etc.⁸⁾

Thus, the composer must

know how to express all inclinations of the heart, by mere choice sounds and their skillful combination, without words in such a way that the listener understands and comprehends clearly the drive, the meaning, the opinion and the emphasis, as if it were a real speech.⁹⁾

It was then the task of the performet („interpret“) to convey this sense of music to the audience and to move them. Türk stated:

You can follow everything … in the most punctual manner … and nevertheless have no good performance, because it still lacks the essential part of it, namely the expression of the prevailing character, without which no listener could be stirred in a high grade. This effect, as the supreme goal of the art of sound, can be produced only when the artist is able to put himself in the ruling affect and to communicate his emotion to others by speaking tones. Expression is thus that part of the good performance, whereby the actual master is mainly distinguished before the common musician. For everything mechanical can finally be learned through much practice; only expression presupposes much other knowledge, besides skill in mechanics, and above all an emotional soul.¹⁰⁾

Aguado, Dionisio held very similar views:

The sublime in art is for the one who plays and performs it to give true meaning to the pieces of music and to disclose in the instrument the ideas of the author so that when the sounds penetrate the ear, they move the hearts of the listeners; this is called expression.¹¹⁾

In Romanticism, however, music was no longer understood as a kind of language, but „as a natural expression of the inner life, without any connection with language“,¹²⁾ and as a means for the music-making and listening individuals, with the participation of their subjective feelings, to blend with the supra-individually common and connecting, i.e., the „beautiful“. Pure music thus represents generalizable emotions:

Mourning and melancholy, moaning and groaning, nostalgia and gentle lamentation are in various degrees a rich stock for the characteristically beautiful expression of pure musical art. … The object of mourning remains indeterminate in the pure art of sound: but the deeper soul of the listener involuntarily adds to the listener's deeper soul its subjective pain, past or present and clarifies it; and this wonderful interweaving of the individual with the universal is due in large part to the unnameable magic of the art of sound.¹³⁾

Mendelssohn Bartholdy, Felix emphasized that musical thoughts can not be grasped in words and that is why they can arouse the same feelings in different people:

People usually complain that music is ambiguous, that it is so dubious what they should think, although everyone understands language. But I feel just the other way around. And not only language as a whole, even single words, even they seem to me so ambiguous, so indefinite, so misunderstandable in comparison to real music that fills your soul with a thousand things better than with words. … The thoughts which music that I love speaks to me are not too indefinite to me to put into words but, on the contrary, too certain. … Ask me what I thought, and I will say: just the song, as it stands there. And if I had a certain word or words in mind for one or the other, then I cannot pronounce them to anyone, because they do not mean the same for one person and another, because only the song can tell the same and can arouse the same emotion in one and the other,—an emotion which does however not express itself through the same words.¹⁴⁾

Eduard Hanslick absolutized this claim in 1854 and stated that music was an expression of the beautiful in itself and therefore an end in itself:

The basic element of music is euphony, its essence is rhythm. Rhythm in general, as the balance of a symmetrical structure, and rhythm in the detail, as the alternating-regular movement of individual parts in the measure of time. The material from which the tone-poet creates, and whose richness can not be thought of lavishly enough, are all of the tones, with the possibility, resting in them, of different melody, harmony and rhythm. Unused and inexhaustible above all abides melody, the basic form of musical beauty; with thousands of transformations, reversals, intensifications, harmony offers ever new foundations; both together are moved by rhythm, the pulse artery of musical life, and they are colored by the charm of a variety of timbres.

If the question is, what should be expressed with this sound material, then the answer is: musical ideas. But a musical idea that has been fully manifested is already independent beauty, an end in itself, and never again the means or material of the representation of emotions and thoughts. The content of the music are tonal moving forms.¹⁵⁾

The artist is inexplorable, the work of art is explorable.¹⁶⁾

What the soulful composer and what the ingenious composer creates, the graceful or the sublime, is first and foremost music, objective structure. Their works will be distinguished from one another by unmistakable peculiarities, and as an overall picture reflect the individuality of their creators, yet they have all been created for their own sake, as one and the other, as independent beauty, purely musically.¹⁷⁾

In the power of music, Hanslick even saw the danger of using it to overwhelm the listener physically. But then it lost its real beauty and became „pathological“:

Musical beauty alone is the true power of the composer. On its shoulders, he walks safely through the torrential waves of the time, in which the moment of emotion offers him no straw against drowning.
You will now see, our two questions—namely, which specific moment characterizes the emotional effect of music, and whether this moment is essentially of an aesthetic nature—are solved by the knowledge of one and the same factor: the intensive effect on the nervous system. This is the basis of the peculiar strength and immediacy with which music is able to excite affections in comparison with any other art that does not produce sounds.
However, the stronger an artificial effect is physically overwhelming, that is pathological, the lower is its aesthetic share.¹⁸⁾

With his warning against overpowering, Hanslick spoke out not least against Richard Wagner and his disciple Anton Bruckner.

Richard Wagner, on the other hand, insisted that music should always be only means to express something outside of music:

Music, which, as an art of expression, can only be true in its fullness in this expression, naturally has here only to refer to what it is meant to express … But music that wants to be more, not just to refer to an object to be expressed, but to fulfill it, i.e., to become this very same object, is basically no longer music, but an absurdity fantastically abstracted by music and poetry, which in truth can only be realized as a caricature. In all wrong aspirations music, really effective music, has really never remained nothing else but expression.¹⁹⁾

This was backed by Friedrich von Hausegger, who portrayed the history of music as Darwinist evolution from the first cry to Wagner's Gesamtkunstwerk and postulated:

The essence of music is expression, purified expression enhanced to the noblest effect. … The sensual pleasure afforded by the play with the sound could not justify the position given to the music. It can be traced back to a pleasant irritation of the nerves, which does not become more valuable in that the remedy which gives rise to it is a precious one, stemming from the strangest complications.²⁰⁾

Music, in this view, becomes the revelation and unfolding of the world in a superhuman sense:

Sounds are not merely phenomena of sensually stimulating effect … They gain an increased interest in revealing properties of the natural world … In nature, timbre itself gains voice. In a piece of music, therefore, we are not merely taught of circumstances which have sprung from the intent of the composer; in them, nature itself becomes loud; it is, as it were, awakened out of its silence and reveals to us qualities of the most wonderful kind. In the sounds elicited from nature, the will that is in it objectifies itself to forms which build the material for the construction of a new world.²¹⁾

Therefore, music is independent of the language:

Music has taken possession of human expression in its original, fluid, form-giving nature. Sound and rhythm, even before they have condensed into words and body, are their elements. It is therefore in a sense correct that music begins where language ends.²²⁾

The goal of music is the perfection of humanity:

The task and high value of art is self-evident. It owes its existence and development to that power which we call love in relation to a particular object. Having sprung from the feeling of union, it keeps it awake by uniting our hearts together in shared emotion. … In this sense, art leads to the purification of passions. It brings to life in us a human ideal which raises us above the impressions of everyday life and works towards our perfection, not through moralizing tendencies, which have nothing to do with the essence of art, but by seizing our innermost impulses and by elevating them to its beauty.²³⁾

The discourse about the musical expression is still not decidable.

Whether or not the reasons behind performance expressivity remain universal across time and culture is a matter for debate. What is more certain is that expressive means can change and have done so radically over time.²⁴⁾

Robert Stecker therefore suggests a „minimalist“ definition:

A musical passage is expressive of an emotion if the best hypothesis of an ideal listener is that the composer intended the emotion to be heard in the music.²⁵⁾
What one has to build into such hearing is a reference to the world of human feeling, i.e., the psychological states such emotion characteristics resemble. This is achieved with the recognition that the characteristics are intentionally placed to make such connections.²⁶⁾

The conceptions of musical expression are clearly different in different ages and cultures. The understanding listening to music therefore does not depend only on physical or psychological conditions. That is why

in summary, we can conclude that listening to music always involves ear training. We learn to listen. Additional knowledge about music can support this learning process and open up further dimensions of emotional experience.²⁷⁾

In the present, therefore, expression—regardless of the difficulty of defining it—still remains a target category of musical creation and understanding.

The purpose of all music training is to teach for musical understanding (to perceive, organize, and then conceptualize what you hear) and consequently to learn how to create musical expression and how to develop an aesthetic response to that expression.²⁸⁾

To escape the danger that such a musical education will become education for a musical elite, Jake Shimabukuro emphasizes the participatory aspects of the ukulele:

You don't have to be a musician to play it. The ukulele is fun, and music should be that way. It shouldn't be intimidating or limited to the people who „have talent.“ Music is the language of emotion. If you know what it's like to feel happy or sad, you can make music.²⁹⁾

• Allen Mathews: Phrasing Strategy: Musical Unity

• Eckart Altenmüller, Reinhard Kopiez: „Starke Emotionen und Gänsehaut beim Musikhören: Evolutionäre und musikpsychologische Aspekte“. In: 16. Multidisziplinäres Kolloquium der GEERS-STIFTUNG 2012; Band 19, S. 55–62.
• Dorottya Fabian, Renee Timmers, Emery Schubert (eds.): Expressiveness in Music Performance: Empirical Approaches Across Styles and Cultures. Oxford University Press 2014