But it isn't the tempo, or the type of instrument, or technical characteristics or form of music that defines jazz. In the hands of a jazz musician, a rhythm, a melody, or a song is filtered through the style of the musician and becomes a personal expression. Because the jazz musician is interested in improvisation and individuality, he will never tell the story quite the same way twice. The notes they play are intended to be as expressive as the rising and falling of a voice or of action during the telling of a story. Musicians from the European tradition were trying to communicate the ideas of the composer of a piece at the expense of their individual sound.
Jazz musicians try to express their own experience through their interpretation of the composition.
Even when jazz musicians compose their own songs, they may express them in different ways from performance to performance, just by the way they play the notes. It's their approach to the music. To illustrate the difference more clearly, lets take a look at a blues based rock musician who had the same basic approach to his instrument as a jazz musician would have. Jimi Hendrix never played the song the same way twice. He was constantly inflecting notes with different resonances, getting different sounds out of his guitar, and he placed a high emphasis on improvisation.