The past several days have comprised a kind of “Larry Keigwin: Welcome to My World” immersion for me. And Mr. Keigwin’s is an odd one indeed. Last week, I saw him do a turn at one of DanceNow’s evenings at Joe’s Pub downtown. On the cabaret stage, he postured under a lamppost, a shutin type who pointed his fingers this way and that, shrinking from the lamp’s exposure. Finally, he turned off the light, and seemed to feel much better for it.