JONI MITCHELL
Unique guitar style...
While some of Mitchell's most popular songs were written on piano, almost every song she composed on the guitar uses an open, or non-standard, tuning; she has written songs in some 50 different tunings, which she has referred to as "Joni's weird chords."
Chelsea Morning
http://www.youtube.com/watch?v=c5DYLYHlKvk

The use of alternative tunings allows guitarists to produce accompaniment with more varied and wide-ranging textures. Mitchell's use of alternative tunings and a highly rhythmic picking/strumming style creates a rich and unique guitar sound. Her right-hand picking/strumming technique has evolved over the years from an initially intricate picking style, typified by the guitar songs on her first album, to a looser and more rhythmic style, sometimes incorporating percussive "slaps", that have been featured on later albums.

In 1995, Mitchell's friend Fred Walecki, proprietor of Westwood Music in Los Angeles, developed a solution to alleviate her continuing frustration with using multiple alternate tunings in live settings. Walecki designed a Stratocaster-style guitar to function with the Roland VG-8 (Virtual Guitar), a system capable of configuring her numerous tunings electronically. While the guitar itself remained in standard tuning, the VG-8 encoded the pickup signals into digital signals which were then translated into the altered tunings. This allowed Mitchell to use one guitar on stage, while an off-stage tech entered the preprogrammed tuning for each song in her set.[37]

Mitchell's longtime archivist, the San Francisco-based Joel Bernstein, maintains a detailed list of all her tunings, and has assisted her in relearning the tunings for several older songs.[37][38]
Mitchell was also highly innovative harmonically in her early work (1966–72) using techniques including modality, chromaticism, and pedal points.[39]
In 2003 Rolling Stone named her the 72nd greatest guitarist of all time; she was the highest-ranked woman on the list.[40]

Big Yellow Taxi
http://www.youtube.com/watch?v=OlNZN94_ ... re=related
Not to mention her innovative & influential jazz fusion work ....
"Herbie Hancock, a longtime associate and friend of Mitchell's, released River: The Joni Letters, an album paying tribute to Mitchell's work. Among the album's contributors were Norah Jones, Tina Turner, Leonard Cohen, and Mitchell herself, who contributed a vocal to the re-recording of "The Tea Leaf Prophecy (Lay Down Your Arms)" (originally on her album Chalk Mark in a Rain Storm).[32] On February 10, 2008, Hancock's recording won Album of the Year at the Grammy Awards. It was the first time in 43 years that a jazz artist took the top prize at the annual award ceremony. In accepting the award, Hancock paid tribute to Mitchell as well as to Miles Davis and John Coltrane. At the same ceremony Mitchell won a Grammy for Best Instrumental Pop Performance for the opening track "One Week Last Summer" from her album Shine."
Talk To ME
http://www.youtube.com/watch?v=oYMQMc3e ... re=related
Jerico
http://www.youtube.com/watch?v=rgEiGJid ... 3439DD7CB8
Off Night BACKSTREET
http://www.youtube.com/watch?v=ke2pBbon ... playnext=2