Jazz musicians added their own twist to the European scales, or group of notes. For example, blues is distinguished by blue notes, and the sound of these note combinations is popular in jazz as well. To understand this, take a piano and find middle C, the note at the center of the keyboard. Now find B - flat. The fifth note up from C. play these two at the same time - what you are playing is called a flat seventh interval. B-flat is the seventh in relation to C, and adds that blues sound to it. Blue, or seventh notes, exist for every note on the piano - not just middle C.
Further departure from the Western chromatic scale (and an arrival at jazz)
Beginning in the 1940s, a lot of jazz musicians began to experiment with more complicated chords and harmonies. Some of these musical combinations aren't found in other forms of music, and they really help give jazz its special sound.
In addition to blue notes, jazz players often use note combinations that can't be produced on a piano. These musicians often bend the note (by bending a string on guitar, or using various techniques on the horns, such as blowing extra had or using a different valve combination), and slide its pitch higher or lower to make a sound that doesn't exist in western chromatic scale. These bent notes help give jazz its mystery, tension, and energy.
Another technique is the use of modes. Modes are various scales, or series of notes. To hear modes, go to a piano and play the C major sale (all the white notes on a piano starting at middle C and ending on the C, one octave higher).
Now, play all the white notes starting on the D above middle C (the white note immediately above middle C) and ending on the D one octave higher. This scale is called the Dorian mode. One can hear other modes of the western chromatic scale by starting the same one-octave scale of all white notes on different notes.
However, understanding modal jazz is a bit more complicated because it can apply to entirely new scales that a jazz musician invents for a particular composition. You may hear the term modal jazz used to describe a new scale being used in a jazz piece even though the scale doesn't figure neatly into one of the traditional modes of western musical theory. You often hear the term modal used to describe jazz that draws from Indian music, which is rooted in scales and modes that help create its centered, meditative sound. In addition, sometimes a group leader may say, "I like these nine notes. Improvise with them any way you want on this tune, but only choose from these notes." That's also modal. And guess what? That's okay, and it's part of the invention and innovation that keeps jazz evolving and exciting.
