It would be easy for bassist Rob Wasserman to be intimidated by the popularity of his current touring partner, guitarist Bob Weir, who usually leads the Grateful Dead on stage. What with the thousands of Dead Heads who follow Weir and his band across the country, who wouldn't be? But while "there are a lot of Grateful Dead fans coming to the shows . . . I wouldn't say it's all his crowd," says Wasserman, 38, who plays the unique Clevenger six-string electric bass that stands 7 feet high. "We're a little more low-key than the Dead." The duo will perform a special acoustic show at MerriweathePost Pavilion tonight. Wasserman said the beauty of the shows for Dead fans is seeing Weir "in a totally stripped down, live performance" "There are no machines," he said. "Just live music and live interaction. Bob can't do this kind of thing with his band. Neither one of us is promoting an album so I always joke that we are the duo with nothing to sell." L Just don't sell Wasserman's contribution to the duo short. A Grammy winner in his own right for the splendid 1988 album "Duets," Wasserman said tonight won't be two hours of "The Bob Weir Show." "I do a 15-minute improvisational bass solo," he said. "We do some Dead songs and some of Bob's old material, but we also enjoy stretching out on some cover songs and standards. We have two full shows worth of material to draw from." After the tour ends in three weeks, Weir will rejoin the Dead, and Wasserman will head back into the studio to make his next record, "Trios." "Trios" will be done in the same vein as his previous effort, which featured his playing with the vocals of Aaron Neville, Bobby McFerrin, Lou Reed and Rickie Lee Jones among others. He has already recorded songs with Edie Brickell and Jerry Gracia (also of the Grateful Dead), and Branford Marsalis and Bruce Hornsby. He plans to have a song with Weir and Bob Dylan, and another with Michelle Shocked and Paul Simon. "This year I've been doing everything but working on the album, Wasserman said. "The last quarter of the year I plan to devote to 'Trios' and hopefully we'll have it out by next spring." * The concert calendar: Merriweather Post Pavilion also has Liza Minnelli (tomorrow), Willie Nelson (Saturday) and Huey Lewis and the News opening with The Subdudes (Sunday). Hammerjacks welcomes White Trash (tomorrow), Wratchild +V America (Saturday), Dan Reed Network (Aug. 10), Three Dog Night (Aug. 13), Badlands (Aug. 17), Southgang (Aug. 24) and White Lion and Saigon Kick (Aug. 25). Pier Six Pavilion has Howie Mandel and Dennis Miller (tonight), Patti LaBelle (Saturday and Sunday), James Ingram and Patti Austin (Tuesday) and The World Beat Tour featuring Ladysmith Black Mambazo and Third World (Aug. 8). The Baltimore Arena hosts the Club MTV Tour, featuring Gerardo, Bell Biv Devoe, Tara Kemp and C&C; Music Factory (Wednesday).