JONI MITCHELL'S greatest gift is not, as one would imagine, her singing, or her words, or her music. Hers is the gift of being uncommonly receptive, first and foremost. The other skills followed on as a natural progression of her ability to grab hold of impressions that pass through her brain and are born in her songs.

Now aged 26, she spent most of her childhood in Saskatoon, Saskatchewan. In fact, just read those last two words aloud, and already you begin to feel some of the early Mitchell influences.

Joni attended Alberta College of Art, and originally wanted to become a professional illustrator, a wish which was not fulfilled until she designed the covers of her three albums. Somehow she got hold of a Pete Seeger "How To Play The Guitar" record, and managed not to learn how to play standard tunings. Which is a good thing, because she began to find her music coming easier with her own unique way of tuning the guitar.

She went to New York for a while, which gave her inspiration to write the songs on her first album, which was in two parts - "I Came To The City" and "Out Of The City And Down To The Seaside". That album was produced by her constant companion at that time, David Crosby.

Joni had already been through one marriage, which lasted "about three weeks," but gave her the knowledge from which to write her biggest-ever song, in which she told about life viewed from "Both Sides, Now."

The song is best-known via the Judy Collins version - but around 125 cover versions are available, ranging from Sinatra and Bing Crosby to Neil Diamond and Pete Seeger. All of which brought the inevitable dollars rolling in to the self-owned Siquomb Publishing company. Enough money to enable her to quit the business completely and retire - which she has done to a certain extent.

Joni seldom works these days. She's not really into all the glamour and schmalz of showbiz, and her Isle of Wight appearance will be the first show she's done since her sellout concert at London's Royal Festival Hall in January of this year.

Joni concentrates on writing and painting these days. She uses the piano more than ever now for composing - witness her latest album, "Ladies Of The Canyon" which is equally divided between piano songs and guitar songs.

She sits for hours on end in her "log-cabin" house high up in the hills of Laurel Canyon, about three miles north of Hollywood's Sunset Strip, sitting at the grand piano in the oak-beamed, wooden-floored lounge. There is no set pattern for tunes or lyrics, first or last. Generally her feelings are translated simultaneously into words and music.

Joni wrote "Willy" about a year ago, just before she and Crosby, Stills, Nash & Young played a one-week season at the Greek Theatre in Los Angeles. It's well-known that Willy is Graham Nash, but the way she puts across the sadness and undecidedness and - strangely - loneliness of Nash, is a prime example of Joni's receptiveness.

She wrote "Big Yellow Taxi" as a warning to so-called civilisation, which can take a paradise like Hawaii and almost commercialise it to death. To Joni, Hawaii is paradise, but she could do without the neon signs, pink hotels with their paved parking lots.

"Marcie," a song on her first album, is about a girlfriend of hers from Canada who came down to live in New York at the same time as Joni. Marcie was in London at the time of Joni's Festival Hall concert, and admitted that everything in the song relates to her trials and tribulations in New York.

It seems that nothing escapes Joni's sensitiveness. She wasn't even at Woodstock, but her pals, Crosby, Stills, Nash & Young were, and she built her own "Woodstock" anthem around the way they all described the scene at the festival. Even Stephen Stills gave up trying to write HIS own version of the incredible happening when he heard Mitchell's, and rushed the group into the studios to record the song even before Joni got her album track completed.

Joni does all her recording at the A & M Records Studios, which used to be Charlie Chaplin's movie lot, because "the piano at A & M is the best in the whole world." She plays and sings most of the parts on her songs, apart from the strings and horns. Although on the chorus of "Big Yellow Taxi" (Shoo, bop-bop-bop-bop) a voice not unlike Nash's can be heard. Joni is really in control of everything that goes on her records. She writes and arranges all the songs, and virtually produces the albums herself, with advice from engineer Henry Lewy.

Joni Mitchell lives for music. Earlier this year, she went to Stephen Stills' birthday party, along with Crosby, Nash, Young and Donovan. Now, that must have been the ultimate vocal super-session!