Jazz is a black American musical form, born in the south in the aftermath of

slavery and the American Civil War. It is an amalgam of several sources:

military marches, black work-songs, and spirituals. African harmony, melody,

and rhythms mixed with European harmony are the main elements of this

musical style.

Jazz unlike other musical genres, is characterized by spontaneity and

flexibility. Consequently, it does not lend itself readily to being written down.

Within a musical structure which is arranged beforehand, the jazz musician is

free to create what is felt.

Since jazz lacks any academic formulas, its performers develop their

natural musical instinct. A player must have superb reflexes and considerable

skill in order to express an original choice of notes. The jazz musician has to

decide with lightning speed which notes to play, whether to play many or a few,

where to pause and for how long, and what to emphasize in order to engage the

listener.

Where in the passage does the author describe how jazz is different from other musical forms?