In 'Guitar' the sense of life comes also from the texture of the surface, prepared with a layer of special plaster painted on while wet, from the physical bite of the incised lines, and perhaps above all from the nervous, bounding, calligraphic quality of the line itself which makes such a vivid presence of the guitar. Nicholson plays a Cubist game with the relationship between the material, wood, of which guitars are made, the fact that the picture is evidently on a wooden panel, and the fact that the wood colour and surface that we see is not natural but beautifully created by the artist. The fluently incised wavy line at the top of the panel serves a decorative compositional function but also describes a distant hilly horizon suggesting that Nicholson has imagined the guitar placed in front of a window. The red-striped white form might be a pottery jug, although its stripes also echo the frets of the guitar. Evidence of the influence of Surrealism on Nicholson at this time, is his description of this work as 'the scratched Surrealist guitar'.
Simon Wilson, Tate Gallery: An Illustrated Companion, Tate Gallery, London, revised edition 1991, p.175