Here are the two main features of jazz.
1) Unlike Western classical music, jazz does not faithfully trace established scores. The performer plays a variation of the melody within the framework of the given harmony. Therefore, it can be said that the performer itself is a composer in a sense. In other words, there is no clear barrier between the composer and the person who interprets it and plays it.
2) The individuality of jazz depends largely on the delicate technique of playing. The essence of jazz is the expression of various performers, including attack, rhythmic strength, intonation, and vibrato.
And the history of jazz cannot be missed without the process of exploring endless harmony. The harmony is built on the tonality framework of major and minor, which was established in the Baroque era (1600-1750). Therefore, any musician must learn the origins of its traditional harmony.
Only then will you be able to sing, accompaniment to performers other than yourself, add harmonies to the melody, and improvise.