WDET-FM (101.9), is dropping four popular interview shows, three specialty music programs and two music-variety shows following the results of a two-year study of audience likes and dislikes, according to WDET station manager Caryn Mathes. "We came to the conclusion that we have several shows that garner great tune-in," says Mathes, "but contribute to audience churn. People tune in, people tune out." Mathes adds that the goal is to generate seamless programming that will hold listeners for hours at a time - rather than losing music fans. Included among the cancelled shows are syndicated National Public Radio programs "Fresh Air with Terry Gross," "Car Talk," The Tavis Smiley Show" and "This American Life."