During 1964, White began to look beyond bluegrass music towards rock 'n' roll as an avenue for artistic expression. Although he was influenced by Country guitarists like Doc Watson, Don Reno and Joe Maphis, he also idolized the playing of jazz guitarist Django Reinhardt, rock 'n' roller Chuck Berry, and studio musician James Burton. White even anticipated the viability of a folk/rock hybrid when, in the summer of 1964, he was approached by Jim Dickson to record a version of the then-unreleased Bob Dylan song "Mr. Tambourine Man" with electric instruments. However, despite White's enthusiasm for the project, he was unable to convince his bandmates in the Kentucky Colonels of the experiment's validity and ultimately, the song was instead recorded by Dickson's proteges, the Byrds.  By the time the original line-up of the Kentucky Colonels folded in late 1965, White had become a respected and well-known guitarist. Abandoning bluegrass temporarily, he switched from his Martin D-28 acoustic guitar to an electric Fender Telecaster, with the intention of becoming a studio musician like his hero James Burton. Transitioning to electric guitar required White to modify his right hand playing technique, switch from open chording to fretting the whole guitar neck with his left hand, and practice using the tone and volume controls. However, he soon mastered the intricacies of the instrument and, between 1965 and 1968, he undertook session work for artists including Ricky Nelson, the Monkees, and the Gosdin Brothers.  As 1965 turned into 1966, White met Gene Parsons and Gib Guilbeau at a recording session for the Gosdin Brothers and shortly after, he began to perform live with the duo in local California clubs, as well as doing regular session work on their records, which were released under the moniker of Cajun Gib and Gene. 1966 also saw White begin playing with a country group called Trio, which featured drummer Bart Haney and former Kentucky Colonel, Roger Bush, on bass. In autumn of that year, as a result of his friendship with Gilbeau, Parsons and the Gosdin Brothers, White was asked to provide lead guitar to ex-Byrd Gene Clark's debut solo album, Gene Clark with the Gosdin Brothers. White also briefly joined Clark's touring band shortly thereafter.  During the Clark album sessions, White reconnected with mandolin player and bassist Chris Hillman, who he had known during the early 1960s as a member of the bluegrass combo the Hillmen. Hillman was currently a member of the Byrds and in December 1966, he invited White to contribute countrified lead guitar playing to his songs "Time Between" and "The Girl with no Name", which both appeared on the Byrds' Younger Than Yesterday album. The country-oriented nature of the songs was something of a stylistic departure for the group and can be seen as an early indicator of the experimentation with country music that would color the Byrds' subsequent work. White also contributed guitar to the band's follow-up album, The Notorious Byrd Brothers, and to their seminal 1968 country rock release, Sweetheart of the Rodeo.

Answer this question "What was session work?" by extracting the answer from the text above.
he undertook session work for artists including Ricky Nelson, the Monkees, and the Gosdin Brothers.