Synesthesis
Synesthesis means "multiple, simultaneous perceptions." The brain is designed for perceiving multiple sensations at the same moment; with the senses of sight, smell, and taste, we expect our sensory experiences to be loaded with multiple, simultaneous stimulations. Even a simple pie is a combination of different flavors from fruit, flour, sugar, salt, spices, eggs, butter, and the effects of cooking. The culinary art lives because people adore eating food that is highly dimensional in flavors. Each dish mingles salty, sour, sweet, bitter, and savory (meaty) in various proportions; and we taste these different flavors on various parts of the tongue; which creates the effect of synesthesia. The senses of sight and smell function similarly. A large measure of the joy of viewing Monet's best paintings is to see all the colors of the palette on every square centimeter of surface. The sense of hearing likewise needs that same level of stimulation. Yet, due to a basic ignorance among musicians about how the ear/brain makes sense of heard experiences, classical music is performed today in a manner due designed to eliminate synesthesia altogether. And popular music is quickly following suit the more the scene accommodates itself to the digital world that is run entirely for money.
Although the many different frequencies and timbres are detected differently by the ears, we 'hear' or perceive musical and other regular, simultaneous sounds as composites, rather than distinct and discreet frequencies and timbres. When music is performed in a way designed to have sounds such as chords be heard as composites, the human ear usually hears only one sound. If the composer has written a four note chord, and all the notes are played simultaneously, the ordinary listener will hear not four notes but one sound only--a rich sound, but nonetheless only one sound. If the performer endeavors to perform each note in the chord so that the notes don't sound absolutely together, the musically untutored listener will easily hear all four notes and the chord simultaneously, creating for such a listener an experience of hearing a total of five sounds altogether.
The synesthesis technique requires heard musical information to be slightly desynchronized, just enough for the mind of the listener to perceive all the timbres, all the pitches, all the melodies, all the rhythms, all the details, and all the harmonies, so that they all emerge into the consciousness of the typical music lover.
It's important to remember that the normal, ordinary human brain is so competent that it has no trouble following as many as 6 simultaneous independent streams of musical information, that is, as long as those lines or streams are functioning with total independence, even if they are "supposed to be together," as in music. For example, there are typically 6 parts in a normal rock group. Rock musicians understand the need for conveying the feeling of independence of parts even when the score would indicate otherwise. They are exceedingly sensitive to synesthetic boredom and work very hard to create synesthesia in their performances...to not do so would spell financial disaster.
In 1768, Jacob Adlung in his Musica Mechanica Organoedi, vol. 2, chapter 22, paragraph 522, says of playing the harpsichord, "One must endeavor to use more arpeggios and such, rather than striking the keys together or playing too slowly since the strings cease vibrating right away." Mozart and Chopin also insisted that the hands are never played together.
The result of having the notes in music be "misaligned in time" is that they are disynchronous. Disynchronicity, when other than an end in itself, produces a kind of independence of voices, and when voices sound truly independent, the brain is able to perceive each individual voice more easily. When we perceive two or more voices or lines as distinct yet simultaneous expressions, the effect in us is called synesthesis. It's an amazing paradox that when the motion of multiple voices are truly independent, the surface appears exceedingly complex but, in fact, the music is far simpler or easier for the average listener to behold and follow. Indeed, the listener feels deprived when the feeling of independence of voices is missing. The synaesthesis technique depends on the ability of the performer to hear, follow, and create multiple voices in the music; voices that are clearly independent of the others yet always manage to agree.
When the lines are played as one usually hears them played today, that is, always together or simultaneously, even a trained musician has trouble to tell the voices apart. This is because the brain reads the interval played in this manner as being a composite. Once so recognized, the brain little needs to pay attention to what is happening except in the lowest or the highest voice. Indeed, very few musicians today have the ability to expressively sing and maintain two voices at the same time...this inability results from a "keypunching" attitude in performing, ironically, an attitude that has now even infected singers. Only by consciously creating distinctions between lines and singing independently each and every voice in the music can the performer make clear to the listener what is happening in music with more than one line. Differences in timbre and volume help create more distinction, but these devices never are as consistently successful at creating clear distinctions between the different lines in music as when the synesthesis technique is used even to only a very slight degree.