Question: What instrument did one of George Harrison's fellow musician co-workers become well known for championing?

Context paragraphs:
Flat Tire: Music for a Non-Existent Movie: Flat Tire: Music for a Non-Existent Movie is the eleventh and final studio album by guitarist Allan Holdsworth, released on 1 December 2001 through Megazoidal Records and reissued on 16 August 2007 through Eidolon Efformation.  Besides the first track, the entire album was recorded by Holdsworth himself using the SynthAxe, an instrument for which Holdsworth had become well known since "Atavachron" (1986).

George Harrison (album): George Harrison is the eighth studio album by English musician George Harrison, released in February 1979.  It was written and recorded through much of 1978, a period of domestic contentment for Harrison, during which he married Olivia Trinidad Arias and became a father for the first time, to son Dhani.  Harrison wrote several of the songs in Hawaii, while the track "Faster" reflected his year away from music-making, when he and Arias attended many of the races in the 1977 Formula 1 World Championship.  The album also includes the hit single "Blow Away" and "Not Guilty", a song that Harrison originally recorded in 1968 for the Beatles' White Album.

Al Jewer: Al Jewer is a Native American flutist from Wisconsin.  He has worked as a record producer and engineer, and as a studio musician, but he has become well known internationally for his work on the Native American flute.  His original training was with the concert flute, and he has been performing classical music with that instrument since the early 1980s.  In 1984, he established Laughing Cat Studio, and in 1994, Laughing Cat Records to give himself control over the recording, production and distribution of his music.  This has given him the chance to work with many other musicians of the Midwestern United States, including Blackhawk, David Storei and Roxanne Neat, Natty Nation, Adrian Belew and Weekend Wages.  Laughing Cat Records currently features artists who perform in Ambient, Native American, Reggae, Classical and Folk.  Al has released two solo albums: "River Crossing" and "Prairie Plain Song" as well as "Two Trees" and "Music of the Earth" (with Andy Mitran).  He also previously formed a duo with Christine Ibach called Cedar Wind.  Cedar Wind released two albums, "Feather on the Wind" and "Kindred Spirits".  His recent music often features harmonies on the alto and bass flute with melodies on the Native American flute.

George Harrison discography: The discography of English singer-songwriter and ex-Beatle George Harrison consists of twelve studio albums, two live albums, four compilation albums, thirty-five singles, two video albums and four box sets (one of which is with Indian classical musician Ravi Shankar).  Harrison's first solo releases – the "Wonderwall Music" film soundtrack (1968) and "Electronic Sound" (1969) – were almost entirely instrumental works, issued during the last two years of the Beatles' career.  Following the band's break-up in April 1970, Harrison continued to produce recordings by his fellow Apple Records acts, notably former bandmate Ringo Starr.  He recorded and collaborated with a wide range of artists, including Shankar, Bob Dylan, Eric Clapton and Gary Wright.

George Harrison – The Vinyl Collection: George Harrison – The Vinyl Collection is a compilation box set by English musician George Harrison, released on 24 February 2017.  The box set contains sixteen vinyl LPs – comprising Harrison's entire output of studio albums from "Wonderwall Music" (1968) to the posthumously released "Brainwashed" (2002), together with the double live album "Live in Japan" (1992) – and two 12-inch vinyl, picture-disc singles. <ref name="Rohrbach/Paste">Paul Rohrbach, "George Harrison Solo Vinyl Box Set in the Works", "Paste", 17 January 2017 (retrieved 4 March 2017). </ref>

If You Believe (George Harrison song): "If You Believe" is a song by English musician George Harrison from his 1979 album "George Harrison".  Harrison began writing the song with Gary Wright on New Year's Day 1978 and finished the lyrics a month later while in Hawaii.  The song appears as the final track on "George Harrison".  Its lyrics are a statement on the power of faith to bring about a desired outcome.

Songs by George Harrison: Songs by George Harrison is a book of song lyrics and commentary by English musician George Harrison, with illustrations by New Zealand artist Keith West.  It was published in February 1988, in a limited run of 2500 copies, by Genesis Publications, and included an EP of rare or previously unreleased Harrison recordings.  Intended as a luxury item, each copy was hand-bound and boxed, and available only by direct order through Genesis in England.  The book contains the lyrics to 60 Harrison compositions, the themes of which West represents visually with watercolour paintings.  Starting in 1985, Harrison and West worked on the project for two years, during which Harrison returned to music-making with his album "Cloud Nine", after focusing on film production for much of the early 1980s.  The book includes a foreword by his "Cloud Nine" co-producer, Jeff Lynne, and a written contribution from Elton John.

Billy Kinsley: William Ellis "Billy" Kinsley (born 28 November 1946, Anfield, Liverpool) is an English musician with The Merseybeats until 1966 (although he temporarily left the band both to form the Kinsleys) The group disbanded in January 1966 to resurface as a duo called The Merseys.  They recorded The McCoys' song "Sorrow" (also covered by David Bowie on his 1973 cover album, "Pin Ups") with the band before embarking on a solo career, where he recorded "Bye Bye Baby".  This song is not to be confused with a Four Seasons track of a similar title, but rather a typical Merseybeat tune.  Followed by the singles: "Annabella", and "You Make My Day".  Kinsley also undertook session work, which most notably included working for Apple Records (alongside George Harrison on at least one song for Jackie Lomax).  He also worked on the popular "Top of the Pops" record series, which contained anonymous cover versions of recent and current hit singles.  During this time he worked with fellow musician friend, Jimmy Campbell, and formed the band Rockin' Horse.  They recorded one album and toured England and Europe as the backing band for Chuck Berry.

Live in Japan (George Harrison album): Live in Japan is a live double album by English musician George Harrison, released in July 1992.  Credited to "George Harrison with Eric Clapton and Band", it was Harrison's second official live album release, after 1971's Grammy-winning "The Concert for Bangladesh".  The album was recorded during his and Clapton's joint Japanese tour in December 1991, and it contains a selection of Harrison's hits as a solo artist alongside some of his best-known Beatles songs.  Aside from the 2001 reissue of "All Things Must Pass", with previously unavailable bonus tracks, "Live in Japan" was Harrison's last release before his death in November 2001.

Ravi Shankar: Ravi Shankar, KBE (] ; 7 April 192011 December 2012), born Rabindra Shankar Chowdhury, his name often preceded by the title Pandit ('Master'), was a Bengali Indian musician and a composer of Hindustani classical music.  He was one of the best-known exponents of the sitar in the second half of the 20th century and influenced many other musicians throughout the world.

Supporting paragraphs: George Harrison discography Ravi Shankar
Answer: the sitar