How New York artists speak to each other - on canvas

Several readers, after returning home from their first gallery-viewing trip to New York, have written to express disappointment in what they found. Where, they want to know, is all the artistic drama and excitement, the dynamic, better-than-ever art they keep reading about in the art magazines? All they saw, they claim, was pretty dull stuff, no matter if it was huge, colorful, and often full of fascinating imagery.

It's not an easy question to answer. These individuals might have come to New York during a particularly dull period, or they might not be sufficiently aware of what goes on under the surface of art to recognize vital new ideas, forms, or movements in their early stages. It is also possible that they don't understand that the New York art scene is similar to a huge and complex dialectical process in which the artistic present is always dynamically ''in dialogue'' with art's past and future. Entering the art world without prior knowledge of what this ''dialogue'' is about is like trying to participate in a debate with only the vaguest notion of what is being discussed.

Art, after all, is a living process of discovery and actualization, and the gallery world represents this ongoing process as well as art's finished products. Most gallery shows are about art, its problems, ideals, and challenges. Only occasionally will one find an exhibition that summarizes an artist's or an art movement's scope or significance, or that gives an accounting of where a major talent stands at midcareer. The vast majority of shows represent works and ideas ''in progress'' and reflect the most recent thinking of artists deeply involved in the larger cultural debate concerning the nature of art - most particularly today's art - and the more immediate problem of creating something both good and significant.

The main point of many first-rate exhibitions may be nothing more dramatic than the artist saying in essence, ''No, I think Stella is a bit too narrow in that area. The real solution lies in this direction.'' Or ''Neo-Expressionism has become too shrill. Maybe it's time I structured my canvases more carefully.'' Neither may sound like much, and the work itself will not be limited to such arguments, but in the hands of imaginative artists, the shows that result may help unblock an art-world stalemate, and help point the way for dozens of other good painters.

It should be clear that there actually are two gallery worlds: one that exhibits finished products - works of art by distant or recent masters (or by artists unconcerned with the dialogue mentioned above) - and another that focuses almost exclusively on the dynamics, the processes of that dialogue. In the former one finds paintings by anyone from Cezanne to Pollock and Wyeth. In the latter, very recent works that may someday hang in museums, or, more likely, be totally forgotten in two years.

The work of four artists with recent exhibitions on West 57th Street and in SoHo here should illustrate my point. Mark Tansey's show at the Grace Borgenicht Gallery provoked a great deal of art world interest. Not for the usual reasons of formal inventiveness or painterly flair (he actually is quite ordinary in both categories), but because of the original and witty manner in which he gives pictorial form to art historical and cultural events and ideas.

''Myth of Depth,'' for instance, explains the awe much of the art world feels for Jackson Pollock's accomplishments. It depicts a small boat crammed with people watching a man walking on water. The man is Pollock, and anyone aware of his art-historical role will know immediately that he is symbolically disproving the Renaissance-inspired dogma that a painting must represent spatial depth if it is to be accepted as a serious work of art. Walking on the water is equated in this work with modernism's insistence that the surface of paper or canvas remain flat, that it not be ''violated'' in order to create the illusion of depth through perspective devices. Pollock is given the hero's role for his dramatic insistence that a painting is a thing entirely unto itself, and not a ''window'' through which the viewer can peer to glimpse a perfectly reconstructed three-dimensional world.

Watching Pollock from the boat are artists Motherwell, Gorky, Rothko, Frankenthaler, and Noland, with critic Clement Greenberg pointing out the significance of what Pollock is doing.

Tino Zago, on the other hand, in his show at O.K. Harris Gallery, continued to tackle an entirely different problem: how to create a powerful and expansive art that fused the best of Abstract Expressionist spatial and painterly qualities with specifically representational landscape elements. As usual, he succeeded brilliantly and proved once again that he is one of the best painters around.

David Salle, one of the art world's current favorites, showed dramatic proof in his recent exhibition at the Leo Castelli Gallery that he no longer is a wild and woolly youth arbitrarily fashioning outlandish combinations out of dramatically incongruous elements. That he is, in fact, fast becoming a serious artist capable of creating strange but effective pictorial metaphors for hitherto unexplored areas of human concern.

And John McNamara, in his second New York exhibition, proved that one can indeed ''change horses in midstream.'' His sudden changeover from strictly nonrepresentational canvases to works incorporating rapidly sketched representational elements is quite logical, however, for it gives him greater control over the profoundly ambiguous and explosive inner realities he needs to actualize on canvas. McNamara may still be a bit raw around the edges, but he is definitely worth watching. His paintings will remain on view at the Bess Cutler Gallery in SoHo through tomorrow.

These, then, are four of the dozens of excellent artists involved at this one moment in time with art's ''great debate.'' Each is a serious painter of uncommon ability, and each has at least a fair chance of ending up in the art history books. Of the four, Tansey presents the most poised and sophisticated attitude toward art, and McNamara the most soul-searching. All should feel proud of their shows, for all proved they could advance their art. And all proved that what they are producing is indeed art.