Alexander Calder and Yves Tanguy -- old friends, drinking buddies and Connecticut neighbors -- are together again. Or rather, their art is, in a delightful, immersive exercise in mutual illumination at L&M Arts on the Upper East Side. Surprisingly, this has never happened before. The L&M exhibition, ''Tanguy/Calder: Between Surrealism and Abstraction,'' brings together 46 works from 1934 to 1956. There are 25 sculptures by Calder, including marvelously ethereal, levitating stabiles and mobiles; some of the wood-and-wire constellations; and three uncharacteristic bronze sculptures. Quite a few of these might almost have walked out of one or more of the 19 paintings and works on paper by Tanguy, some of which even include startlingly Calderesque wire structures, and nearly all of which depict oddly shaped, water-worn stones in amalgams that suggest human involvement, albeit long past. Stonehenge for pebble lovers. These formations, in varying densities, occupy vast plains that recede in increasingly atmospheric, horizon-free gradations of land, mist and sky. The colors often have a warm sunset glow -- if not a lurid afterglow. [ABSTRACT FROM PUBLISHER]