Waterfowlers for generations chattered, chortled and chuckled in earnest, if sometimes erratic, effort to mislead ducks into thinking friend rather than foe awaited them in the blind below. Now all is changed. Sporting goods counters overflow with dozens of artificial calls, many of which can be mastered in minutes. And if a hunter doesn't want to use his lungs, there are manually operated duck and goose calls. The Scotch duck call, for example, is so easy to use that the manufacturer suggests jiggling it with one foot if both hands are otherwise occupied. But for all the simplification, making exactly the right sound at the right time takes practice. This problem, however, is being solved, too, with the sale of instructional records guaranteed to teach the neophyte everything from the fundamentals of breath control to advanced duck discourse.