You can't touch it, you can't eat it, and you can't see it. So, why do we enjoy music so much? So much in fact that we spend billions of dollars each year buying records and equipments to play it back.

Why do we like music? Our culture immerses us in it for hours each day, and everyone knows how it touches our emotions, but few know how music touches other kinds of thought Slow music promotes rest, meditation and a sense of well being. It is used in elevators to keep people calm in close quarters. Quicker rhythms make us move faster, which is why light, rapidly paced music is used in stores -- to get us to actively look at the products and buy more. Very fast and loud music arouses, agitates, and energises us. Just as in a military march, loud rock music, can get our own hearts beating faster. Sometimes, we use music as a trick to misdirect our understanding of the world. When thoughts are painful we have no way to make them stop. We can attempt to turn our minds to other matters, but doing this just submerges the bad thoughts. Perhaps music can tranquillise by turning under-thoughts from bad to neutral, leaving the surface thoughts free of affect by diverting the unconscious Doctors recommend laying a crying baby on its mother's chest. Why? So the baby can hear the familiar, restful and secure sounds that are such music to its ears.

That musical pleasure can be described partly by numbers is a discovery most commonly attributed to Pythagoras, the Greek mathematician who was the first to develop a mathematical theory of consonance.
Pythagoras used an instrument called the monochord, which consists of a string whose length can be varied without changing its tension. He observed that certain combinations of string lengths (different pitches, or notes) sounded better together than others. This relationship is called consonance and describes how well multiple tones sound when played at the same time. A set of tones played as such is called a chord. Pythagoras discovered that if the ratio between the tones in a two tone chord is 2:1, or 1:2, then the tones are very consonant. This ratio is called an octave, and is equivalent to a 440Hz tone with a 220Hz tone, a 300Hz tone with a 600Hz tone, etc. In modern musical notation, notes an octave distant from each other have the same name (letter). For example, a 440Hz tone is an A, but so are 110Hz, 220Hz, 880Hz, 1760Hz, etc. This is because notes an octave apart are so consonant that the ear often fails to note much distinction between them. Pythagoras observed that ratios such as 3:2 and 4:3 are also consonant. This led to his theory that the most consonant tones are those whose ratios have factors of 2 and 3. This was the first known example of a law of nature ruled by the arithmetic of integers, and greatly influenced the intellectual development of his followers, the Pythagoreans .

The most prevalent current theory of consonance is that it is based upon overtones, which are decreasingly audible tones heard when a tone is played on an instrument. These tones exist at frequencies which are integer multiples of the fundamental. For example, a tone played at 100Hz will have overtones at 200Hz, 300Hz, 400Hz, etc. The theory states that a correlation in overtones causes consonance, while a slight difference in overtones causes roughness, or dissonance. For example, a tone played at 200Hz will have a second overtone of 600Hz. This will correspond with the first overtone of a tone played at 300Hz, thus indicating a consonant relationship. It is a necessary basic assumption of this theory that tones without overtones (i.e sine waves, which are very difficult to produce without using a computer) do not exhibit a difference in consonance unless their frequencies are close to each other.
Euler developed a theory of consonance which is independent from overtones. Euler's theory states that the consonance, or degree of sweetness,of a chord depends upon the consonance of the integers of the ratio of the frequencies. The consonance of an integer depends upon the number and size of its prime factors, where fewer, smaller primes lead to a more consonant tone.

 

[ Melody ]

These various solutions to consonance and harmony are a success in the scientific study of music; however, they do not provide a great deal of insight into the greater problem of melody. Whereas harmony represents a certain instant of time, melody involves continually changing pitches over time. There are 167545823917329926683629711637865880974548517628774818744410515 76771566163132284530189242543898624 possible 50-note melodies. The most significant difference between scientifically studying harmony and melody lies in the fact that, while harmonic relationships have not been observed to change significantly with different cultures and time periods, there seems to be little or no relationship between many melodic structures of different cultures and ages. Indeed, the common phrase, "music is a universal language,"can hardly be true when the entire manifestation of melody varies greatly from culture to culture (Dobrian N. Pag.). Greek music, for example, offers little aesthetic pleasure to the modern (western) ear.
Fortunately, the flexible nature of melody does not make it entirely elusive to scientific study. There are fundamental principles of language and how it develops, even though it varies greatly in its manifestation. Likewise, there are similar fundamental principles which are observable in music. One widely accepted theory of music, proposed by Leonard Meyer, contends that the enjoyment of music comes from the blending of expectation and surprise (Allman 62). The idea is that a predictable melody deprives the listener of stimulation, and instigates boredom, while an unpredictable melody lacks coherence and also leads to boredom. An ideal melody, thus, must exhibit a certain ideal amount of order which is between absolute order and absolute chaos. No one can credibly claim that the pleasure of specific music is universal (the same in every person), because it obviously is not, but it is doubtful that this is due to a significant difference in the way people's minds work. All cultures do enjoy music, even if the type of music varies widely from culture to culture. Because of the universality of the enjoyment of music, there must be some aspect of the mind which registers pleasure based on abstract sensual input (abstract meaning input that has no obvious correlation to pleasure). It is the nature of this aspect of the mind (the aspect that associates certain abstract input with pleasure) that is in question. One theory is that it is based on fulfillment of unconscious desire, which supports Meyer's ideas because one cannot fulfill a desire without first creating it, and the creation of desire can hardly be desirable.

Unfortunately, a theory that successfully and thoroughly explains why we enjoy music does not exist. If such a theory did exist, it is unlikely that music would continue to be an art form as we know it. For example, if a theory explaining the nature of music became known, it would likely be possible to use this theory to derive good music algorithmically, eliminating the need for composers. Attempts have been made at such derivation, using a variety of different algorithms.