Forget the bootleg T-shirts, the TV ads for Butterfinger candy bars, the forthcoming Christmas book, and commercial pinball machine. The latest and most eagerly anticipated Simpsons-abilia is The Simpsons Sing the Blues, an LP expected from Geffen Records. Shrouded in secrecy, the project, which reportedly features a number of high-profile guest stars and at one time was scheduled to include Michael Jackson and M.C. Hammer singing along with the Simpsons, has had its release date bumped up from Dec. 4 to Nov. 27. While a Geffen spokesperson admits being ”afraid of saying the wrong thing” because the album is ”a delicate thing for us,” the company has divulged a few details: Linda Ronstadt’s producer, John Boylan, is twiddling the knobs while primo L.A. saxophonist Tom Scott plays Lisa Simpson’s solo on ”Springfield Soul Stew,” which features mother Marge’s vocal debut. Geffen says that Bryan Loren, a ”close personal friend” of Jackson, is producing a rap song, ”Do the Bartman.” Also expected to take part is former punk rocker turned lounge lizard Buster Poindexter.