Who was regarded as the first free jazz musician?
Although free jazz is widely considered to begin in the late 1950s, there are compositions that precede this era that have notable connections to the free jazz aesthetic. Some of the works of Lennie Tristano in the late 1940s, particularly "Intuition", "Digression", and "Descent into the Maelstrom" exhibit the use of techniques associated with free jazz, such as atonal collective improvisation and lack of discrete chord changes. Other notable examples of proto-free jazz include "City of Glass" written in 1948 by Bob Graettinger for the Stan Kenton band and Jimmy Giuffre's 1953 "Fugue". It can be argued, however, that these works are more representative of third stream jazz with its references to contemporary classical music techniques such as serialism.
Who was the first jazz musician that exhibited free jazz techniques?
Lennie Tristano
Free jazz
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Free jazz effectively began with groups led by who?
Ornette Coleman
Free jazz
https://en.wikipedia.org/wiki/Free%20jazz
Ornette Coleman rejected pre-written chord changes, believing that freely improvised melodic lines should serve as the basis for harmonic progression. His first notable recordings for Contemporary included Tomorrow Is the Question! and Something Else!!!! in 1958.[9] These albums do not follow typical 32-bar form and often employ abrupt changes in tempo and mood.[10]
Free jazz
The free jazz movement received its biggest impetus when Coleman moved from the west coast to New York City and was signed to Atlantic. Albums such as The Shape of Jazz to Come and Change of the Century marked a radical step beyond his more conventional early work. On these albums, he strayed from the tonal basis that formed the lines of his earlier albums and began truly examining the possibilities of atonal improvisation. 
Free jazz
Although free jazz is widely considered to begin in the late 1950s, there are compositions that precede this era that have notable connections to the free jazz aesthetic, which include some of the works of Lennie Tristano in the late 1940s, particularly "Intuition", "Digression", and "Descent into the Maelstrom" exhibit the use of techniques associated with free jazz, such as atonal collective improvisation and lack of discrete chord changes. Ornette Coleman rejected pre-written chord changes, believing that freely improvised melodic lines should serve as the basis for harmonic progression. His first notable recordings for Contemporary included Tomorrow Is the Question! and Something Else!!!! in 1958, these albums do not follow typical 32-bar form and often employ abrupt changes in tempo and mood. The free jazz movement received its biggest impetus when Coleman moved from the west coast to New York City and was signed to Atlantic, and made albums such as The Shape of Jazz to Come and Change of the Century, which marked a radical step beyond his more conventional early work because he strayed from the tonal basis that formed the lines of his earlier albums and began truly examining the possibilities of atonal improvisation. 