The high-tech lowlifes who rip off music from the Web may have finally met their match. So far, rampant piracy has hampered the secure selling of tunes online. But now a snarling digital watchdog is hounding the bad guys: Unveiled in July on Music Boulevard, a New York-based online CD retailer (http://www.musicblvd. com), N2K’s e_mod (encoded music online delivery) enables Web surfers to download Dolby-quality singles by selected artists for 99 cents a pop. Encryption and digital watermarking systems will allow one-time transfer to a CD but prevent multiple downloads and trademark infringement of the tunes. Security types believe that e_mod and similar antipiracy processes have the potential to open a huge trade in music over the Internet while offering ease and accessibility to mouse mixers. Next up, Knitting Factory Works (http://www.knittingfactory.com) debuts its own music-delivery system late this summer.