The essence of traditional jazz is that a lead instrument will play the melody of a tune, and then improvise on it, whilst other instruments in the ‘front line’ will play variations or paraphrases of it at the same time. This creates a polyphonic effect. which is sustained whilst other instruments take their turn to improvise their solos.

Modern Jazz:
Instrumentation retained what had become the classic quintet format of piano, bass, drums, and two lead horns. And the approach to musical content remained focussed on playing a melody, then improvising on its harmonies.

However, around this time some musicians started to use modal concepts of harmony, which meant using scales rather than a sequence of chords. Two of the main exponents of this approach were Miles Davis and John Coltrane. The video that follows features one of the earliest compositions of this klind – So What. In the years that followed, both musicians went on to develop this approach much further.
7. Jazz musicians use the term "lead" or "head" to refer to the main melody, which is used as a starting point for improvisation.
For a big band (10 or more instruments), the structure is similar, but because there are so many players, more of the music must be written out ahead of time to keep everybody organized. In jazz, when portions of the music are composed ahead of time, it is called an arrangement.
Jazz rhythms can range from simple to extremely complex.
8.

9. 

10. Jazz traditionally applies the following tempo markings:

slow | 48 -60 bpm
medium slow | 60-90
medium | 90-140
medium fast | 140-180
fast | 180-240
up-tempo | 240 - 340
The following are some of the expression marks which occur most frequently in music :

Jazz musicians don’t syncopate ALL the time (if they did it would be monotonous). Instead, jazz music involves both syncopated and non-syncopated notes -- just which ones to syncopate is up to the player and, once they get good enough, they do this intuitively (that is, without having to think about it; just like fluctuating your voice when talking so you don’t talk in a monotone). 
2. A great composition and a great solo have the same musical qualities: a well-crafted melody, interesting rhythmic content, and a logical flow of harmonic motion. Refining these musical devices and sounds through composition will directly translate to your playing the next time you take a solo.
Scales and chords made sense on paper, but when it came to improvising that knowledge just wasn’t cutting it. An intellectual understanding of music theory is one thing, but when you have to put these tools to use creating melodies and harmonies you need an in-depth knowledge.

3. At the most basic level melody, harmony, and rhythm must be combined with the sounds that you’re hearing in your head to create music. It’s as simple as that. Composing is improvising and improvising is composing. And logically, studying and improving at one will greatly benefit the other.
4. A common misconception about Jazz improvisation is that it's invented out of the air. This notion may exist because many small Jazz groups do not read music when they perform. Jazz players will choose phrases that seem to be preordained so you intuitively know where they are going, even though it's being created at the instant you are hearing it. The musicians are actually spontaneously creating a very intricate form of theme and variation; they all know the tune and the role of their instrument. The guitar, piano, bass and drums, while all able to solo, basically provide the rhythm and harmony over which the soloist will create improvised variations. The structure is flexible so that the soloist may venture in various directions depending on the inspiration of the moment. A Jazz musician is creating spontaneous art every time he or she plays music. In fact, spontaneity has always characterized Jazz music's finest improvisers.
5. A sharp note can be defined as a raised pitch, or more specifically, a natural pitch that is raised to the next consecutive pitch. The 'Jaws Theme Song' makes great use of sharp notes since it continually starts on a pitch, then is raised to the next closest pitch. The sharp symbol looks something like a number sign or like a Twitter hashtag. The sharp symbol notifies us of a change in the usual condition of things.
A flat note is basically the opposite of a sharp note, in that it is a lowered pitch, or more specifically, a natural pitch that is lowered to the next consecutive pitch. Much like a flat tire, a flatted note goes down. The flat symbol looks like a pointy lower-case letter B or almost like an arrow pointing down.
There is one exception to the rule of accidentals within a measure. A sharp or flat can be canceled out by a special symbol called the natural sign. If we add a natural sign to the last note of our previous example, it would look like this. This would mean that the last note would be played as B natural because the flat sign is no longer in effect.
6.  By providing the brain with an 
artificial environment, and forcing it through that environment in 
controlled ways, music imparts the means of experiencing relations far 
deeper than those we encounter in our everyday lives.  When music is 
written with genius, every event is carefully selected to to build the 
substructure for for exceptionally deep relations.  No resource is 
wasted, no distractions are allowed.  Thus, however briefly, we attain a
greater grasp of the world (or at least a small part of it), as if 
rising from the ground to look down upon the confining maze of ordinary 
existence.
7. 

The treble clef is also called the G clef because it

Your left hand typically plays the lower notes on the keyboard, which are also called bass notes. 
8. Jazz is a music genre that originated in African American communities of New Orleans, United States,^]in the late 19th and early 20th centuries, and developed from roots in blues and ragtime. Since the 1920s Jazz Age, jazz has become recognized as a major form of musical expression. It then emerged in the form of independent traditional and popular musical styles, all linked by the common bonds of African American and European American musical parentage with a performance orientation.Jazz is characterized by swing and blue notes, call and response vocals, polyrhythms and improvisation. Jazz has roots in West African cultural and musical expression, and in African-American music traditions including blues and ragtime, as well as European military band music. Although the foundation of jazz is deeply rooted within the black experience of the United States, different cultures have contributed their own experience and styles to the art form as well. Intellectuals around the world have hailed jazz as "one of America's original art forms".

Variety's headline after the Crash
The tremors that would eventually destroy this flimsy economic edifice made their first rumblings in September 1929. The market dropped sharply at the beginning of the month but rose again only to drop and rise again. The rollercoaster ride continued in October as the beginning of the month saw another drop followed by another burst of strength. Then came Black Thursday – October 24 – when a drop in stock prices triggered a burst of panic-selling so frantic that it overwhelmed the Stock Exchange's ability to keep track of the transactions.

Wall Street financers were able to reverse the downward plunge only by buying as many shares of stock as they could over the next two days. It was a temporary victory. Monday's opening bell unleashed a frenzy of selling that soon turned into an uncontrolled panic that continued for the rest of the trading day. The following day – Black Tuesday, October 29 – saw the previous day's panic turn into bedlam on the trading floor.

According to one observer, traders "hollered and screamed, they clawed at one another's collars. It was like a bunch of crazy men. Every once in a while, when Radio or Steel or Auburn would take another tumble, you'd see some poor devil collapse and fall to the floor." This was the Crash, although few could see it at the time. The Market continued its decline but never as dramatic. Thirty billion dollars had been lost - more than twice the national debt. The nation reeled, and slipped into the depths of the Great Depression.

In the early years of jazz, record companies were often eager to decide what songs were to be recorded by their artists. Popular numbers in the 1920s were pop hits such as "Sweet Georgia Brown", "Dinah" and "Bye Bye Blackbird". The first jazz artist to be given some liberty in choosing his material was Louis Armstrong, whose band helped popularize many of the early standards in the 1920s and 1930s.

Some compositions written by jazz artists have endured as standards, including Fats Waller's "Honeysuckle Rose" and "Ain't Misbehavin'". The most recorded 1920s standard is Hoagy Carmichael and Mitchell Parish's "Stardust".Several songs written by Broadway composers in the 1920s have become standards, such as George and Ira Gershwin's "The Man I Love" (1924), Irving Berlin's "Blue Skies" (1927) and Cole Porter's "What Is This Thing Called Love?" (1929). However, it was not until the 1930s that musicians became comfortable with the harmonic and melodic sophistication of Broadway tunes and started including them regularly in their repertoire.

In 1920, the jazz age was underway and was indirectly fueled by prohibition of alcohol. In Chicago, the jazz scene was developing rapidly, aided by the immigration of over 40 prominent New Orleans jazzmen to the city, continuous throughout much of the 1920s, including The New Orleans Rhythm Kings who began playing at Friar's Inn.However, in 1920, the cabaret business began in New York City and the growing number of speakeasies developing in the cellars of New York City provided many aspiring jazz musicians with new venues which gradually saw many musicians who had moved to Chicago ending up in on the east coast. It is important to note that Classic Blues became very prominent from 1920 after Mamie Smith recorded Crazy Blues and grew in popularity along with jazz.

In 1920, Paul Whiteman and his band recorded Whispering in New York City, in a subgenre known as symphonic jazz. Meanwhile, in New York City Adrian Rollini began playing bass saxophone with the California Ramblers and would later in the decade play with Bix Beiderbecke. Duke Ellington had developed in a successful band leader and Louis Armstrong began to amaze audiences with New Orleans Jazz.