The improvisational nature of jazz musicianship is such that a truly competent performer must be prepared to function as an on-the-spot composer who is expected to contribute to the orchestration in progress, not simply to execute the score as it is written and rehearsed.
Jazz music, as is also the case with the old down-home spirituals, gospel and jubilee songs, jumps, shouts and moans, is essentially an American vernacular or idiomatic modification of musical conventions imported from Europe, beginning back during the time of the early settlers of the original colonies.
Effective stream-of-consciousness narration is the product of verbal precision, not just of literal documentation. It is decidedly not a matter of unedited free-association.
As any competent student of literary composition knows, the more natural and casual a voice sounds in print, the more likely it is to have been edited time and again.
When the Negro musician or dancer swings the blues, he is fulfilling the same fundamental existential requirement that determines the mission of the poet, the priest and the medicine man.