AS the artist recounted it, (first to Kahnweiler and, later, in more detail, to me), the solution for the representation of the sound-hole of the ''Guitar,'' a cylinder projecting from the back plane, came to him from Grebo masks. The front plane of the ''Guitar,'' though present at the bottom and on the right, is cut away in the center of the ''instrument.'' The problem might be stated thus: how to signal a hole in a plane (the front of his ''Guitar'') that does not literally exist? The solution was, as in the Grebo mask, to turn negative into positive and project the hole forward as a hollow cylinder. The very hollowness of Picasso's cylinder had already been anticipated in the circular rims painted on the front of the eye-cylinders by the Grebo artist.
Now this solution of Picasso's was entirely consistent with his other syntactical decisions in the making of the ''Guitar,'' not to say with the whole fabric of determinations that implemented Synthetic Cubism, all of which followed their own inner logic. It would be foolish, therefore, to overestimate the importance of this particular and limited intervention of tribal art even in an object that launched a sculptural revolution. Perhaps more important than its particular contribution to the ''Guitar'' is the way this intervention testifies to the underlying affinity between tribal and modern art on the level of conceptual form, and the evidence it gives of how certain kinds of modernist readings endowed tribal objects with a special resonance in the Cubist period. This particular ''formalist'' reading - and many readings of tribal objects by Picasso and other modernists were anything but formal - probably had nothing whatever to do with what the African artist was getting at, though, to be sure, we do not know what artistic intuitions motivated the artists who invented the Grebo style. To insist that these sculptors usually functioned within a framework of religious needs and values says nothing that would not be largely true for certain Western styles, and still left them with the problem of plastic solutions - even though they had no concept for what such words mean.
Compared to some other Grebo masks, which began to be available at the turn of the century (Picasso would have seen the fine one that entered the Trocadero in 1901), the Picasso Grebo reproduced above is a routine work of art. (Another, possibly acquired in 1912, is much finer; it is shown hanging on a wall of Picasso's apartment in a drawing of 1917.) Given what we know of Picasso's attitudes toward tribal objects, however, we should not be surprised that he prized it highly despite its mediocrity; after all, its ''idea'' is completely clear. It is instructive, nonetheless, to compare this lesser of Picasso's Grebo masks to one made by an inspired sculptor, such as that in the Metropolitan Museum. The basic Grebo stylistic constituents - a ''slat'' nose without nostrils, cylindrical eyes, and parallel lips, all projecting at right angles from a generally flat panel - are common to both. And yet what a difference! The Metropolitan example is not only subtler in the proportioning and distribution of the common elements, and in its use of color, but in the very slight convexity given the main panel. Moreover, it contains what may be a truly artistic leap of the imagination. Rather than representing the horns, the artist has absorbed their curve into the exquisite elongation of the panel, where they are present only inferentially. (The degree of this artistic ''leap'' would depend, of course, on such masks, unknown in the West, as might have mediated between horned Grebos like Picasso's and the Metropolitan example.)
It is still sometimes said that traditional tribal art was a collective rather than an individual creation involving constant repetition of established formulae, to which the individual carver brought little beyond artisanal skill. My own experience with this art, on the contrary, has confirmed for me the assumption that good art is made only by gifted individuals. I am, in fact, struck by the differences rather than the similarities between tribal pieces of the same style (at least in types not standardized for European taste), and especially by the uniqueness of those works I would call masterpieces. For example, of the dozen or so Grebo masks I have seen, no two are alike, though all include the basic constituents. And the Metropolitan's, the finest of the group, is the least typical. The differences between these masks are just as marked as those between works by anonymous Western artists of the Medieval schools in given regions - any particular school of Romanesque sculptors, for example. And the best work of both is distinguished by unique qualities of expressiveness and invention. That sculptures as fine as the Metropolitan's Grebo mask are, indeed, rare among Primitive objects, that the overwhelming bulk of tribal art is not very good, says nothing about it that would not be true of the production of any period, including - if not especially - our own.