When Bob Dylan's first major US exhibition of original artwork opened at the Gagosian Gallery in New York on 20 September, critics were united in their relief that the assembled paintings were, if not groundbreaking, not as awful as the science-based lithographs of the former Monkees front man Micky Dolenz. Or as dull as the Rolling Stones guitarist Ronnie Wood's portraits of . . . er, the Rolling Stones. Some rock musicians are true renaissance men, with creditable work across several mediums, but those who fit such a description can probably be counted on one hand (Don Van Vliet, better known as Captain Beefheart, has claim to a finger).

Dylan has long been a graphic artist. In the first (and as yet only) volume of Chronicles, his semi-fictionalised memoirs, he describes how he "picked up the habit" of drawing from the late Suze Rotolo, his girlfriend in the early 1960s: "I would start with whatever was at hand. I sat at the table, took out a pencil and paper and drew the typewriter, a crucifix, a rose, pencils and knives and pins, empty cigarette boxes." This interest would manifest itself sporadically throughout his career, with his visual work adorning the album covers of the Band's Music from Big Pink (1968) and his own early 1970s releases Self Portrait and Planet Waves.

In 2008, the Statens Museum in Copenhagen exhibited a large collection of his paintings called "The Brazil Series", supposedly based on Dylan's personal observations of the country on his travels. The Gagosian's show, "The Asia Series", is a sister project that takes south-east Asia as its subject. (The gallery's somewhat po-faced blurb claims that it is a "visual journal" that "comprises first-hand depictions of people, street scenes, architecture and landscape".) Despite its foreign themes, the exhibition represents an artistic homecoming for Dylan, whose compulsive image-making began in the nearby bohemian quarters of Greenwich Village, under the wing of Rotolo.

"The Asia Series", however, has been controversial for Dylan's unapologetic use of appropriated compositions: fans on the forum pages of the Expecting Rain website have identified the source images of several of the paintings, including a photograph of an elderly Chinese man and a friend by Henri Cartier-Bresson, taken in 1948. Perhaps even Johann Hari would blush at the scale of Dylan's direct referencing of other people's work -- from the central figures to the incidental background details, the artist seems to have faithfully reproduced every detail.

Michael Gray, author of the Song and Dance Man series of books on Dylan, was withering in his analysis: "[It] may be a (very self-enriching) game he's playing with his followers but it's not a very imaginative approach to painting," he wrote on his blog. Yet is Dylan's approach to painting so surprising? His work throughout his career -- in song, poetry and film, as well as visual art -- has been characterised by an exhilarating omnivorousness. The restless, mercurial energy of his music is partly derived from how each of his songs contains multitudes of other voices.

Folk music is an adaptive vernacular: it survives by evolving. Much of this process takes the form of one musician borrowing a line or verse from another and adding something new along the way. In the song "Trouble in Mind", Big Bill Broonzy sings: "I won't be blue always/Yes, the sun gonna shine/In my back door someday." In "Big Road Blues", the ever mysterious Tommy Johnson sings: "Lord, sun gon' shine in my backdoor, someday/A wind gon' change all blow my blues away." Such "floating lyrics" belong to no one and pass from one songwriter to another; their expressive power draws from their mutability, the sense that their meaning is at once unfixed and specific, that their significance is simultaneously personal and communal.

Dylan has applied the methodology of the maverick phrase to all of his output, from lifting a Bascom Lamar Lunsford line ("A railroad man, they'll kill you when he can and drink up your blood like wine") for his song "Stuck Inside of Mobile with the Memphis Blues Again" ("They say that all the railroad men drink up your blood like wine") to piecing together fragments of Jack London novels and articles from Time magazine to colour his memoirs. His 2001 album Love and Theft was a manifesto in practice that celebrated pastiche as a liberating strategy: the final song, "Sugar Baby", took the melody and parts of the chorus from the 1927 show tune "Lonesome Road" by Gene Austin and Nathaniel Shilkret, for instance, and even the name of the collection was a nod to the historian Eric Lott's excellent book about minstrelsy of the same name.

Is pastiche, this loving theft, something that detracts from the quality of an artwork? Jacques Derrida's notion of iterability posits that a set of signs carries meaning because it is repeated, and that it cannot be saturated by any one context. Dylan's work, be it his painting, his music or writing, enacts this freedom from single interpretation, and that's why, for me, the best of it is endlessly rewarding. By repeating and assembling pieces of our shared cultural heritage, Dylan offers us a reflection not only of these new dark ages, these modern times, but also of the creative journey that has brought us here.

The Gagosian show may well be patchy -- Dylan's craftsmanship as a painter is unremarkable -- but to dismiss him for, in effect, applying the folk method to the canvas is unfair. Besides, has he been disingenuous? In the interview included in the exhibition catalogue, he says: "I paint mostly from real life. It has to start with that. Real people, real street scenes, behind the curtain scenes, live models, paintings, photographs, staged setups, architecture, grids, graphic design. Whatever it takes to make it work." The implication is that, to Dylan, photographs and paintings are as "real" as people and street scenes. In a hyper-mediated world, the media artifact is surely valid as a source of inspiration.

Hat-tip to Neil Rennie, from whom I borrowed (appropriated? referenced? stole? pastiched?) the Tommy Johnson/floating line example.

Yo Zushi works for the New Statesman. His work as a musician is released by Pointy Records