One of the most characteristic traits of jazz as it was originally conceived, is the special way in which the instruments are played: the sounds, the intonations, the way the notes are linked or separated, how they are distorted, how they are held or kept in vibrato, all have very little to do with how instruments are played in classical music and are far from the manner of playing that is taught in music schools and conservatories. It is clear that jazz music, as it is usually played by jazz men and jazz women, would not receive approval from a jury of academics.
However, for those listeners that are not overly conditioned by the prescriptions and prejudices of orthodoxy, the sounds that jazz musicians extract from their instruments are able to communicate a type of emotion and experience that is difficult to find in other musical genres. The expressivity that jazz men and women of a certain category are able to draw out of their instruments can be very special and remarkable.
The root of this very particular expressivity lies in the fact that jazz musicians play with an instrumental technique, that is not academic, and which is inspired directly by the expressive resources of African-American singers, specifically the way they interpret the sacred Gospel Songs and the profane Blues. These songs owe their ability to move listeners to certain vocal resources, such as: the dry note attack, the vocal inflection, the rapid vibrato held at the end of notes, the guttural sound (known as growling), etc. All of these resources, used by both African-American preachers as well as Blues singers, have been adopted by jazz musicians who incorporated it into and allowed it to define their manner of playing, so that they each have their own instrumental technique, that may not be very orthodox, but which provides results that are clear and beyond any discussion. So, the musicians of jazz attack notes with force, they work the inflections, they hold the notes and finish them with rapid vibrato, and they can even give them a hoarse, growling sound in imitation of Blues and Gospel singers’ guttural singing.
Furthermore, their way of working with and focusing on instrumental technique without allowing themselves to be subject to rigid rules makes each individual jazz musician have their own personal technique that gives them a sound and ways of expressing themselves that is completely unique, a sound that is absolutely identifiable and differentiable from other jazz musicians. That means that if we are a little familiar with their music, we can identify the musician just from the sound he is able to extract from his instrument, just as we are able to identify someone we know from the sound of their voice.
Ricard Gili, Fundació Catalana Jazz Clàssic