TV themes losing place in prime time

I don't remember much about high school biology or physics, and I couldn't tell you how to compute a calculus problem, but, for the love of Will Smith, the theme song to "The Fresh Prince of Bel-Air" remains fresh in my mind.\nSmith's catchy rap opened each episode of his hit '90s sitcom, in which he starred as a street-smart teen from Philly who moves in with wealthy relatives. A whole generation knows the rap by heart, as well as the "Saved by the Bell" song.\nTV themes, from "The Beverly Hillbillies" to "The Brady Bunch" to "Cheers" to "Friends," conjure up memories of cozy nights, childhood bliss and a universal nostalgia for bygone days. Today, show themes are doing a fast fade as the networks crunch their programming budgets.\nAre they about to join the variety hour in the TV graveyard?\n"It's a rarity today," TV historian Tim Brooks said of the catchy, tuneful opening. "It's kind of like the Broadway musical producing hit songs -- it just doesn't do that anymore."\nBack in the day, even into the '90s, shows usually had a "main title," a 40- to 60-second opening montage that introduced the cast and was set to music written by a composer, said Jon Burlingame, author of "TV's Biggest Hits," a history of themes. Songs summed up what a show was all about, whether spinning the tale of how a group of wacky castaways ended up on "Gilligan's Island," telling how a spunky single career woman was "going to make it after all," or describing why six touchy-feely Manhattan singles were there for each other.\nNow, many shows -- like ABC's "Lost" are using less musical statements to open shows. \nWill Smith, back in the '90s, made a statement of his own while advising fans to "just sit right there/I'll tell you how I became the prince of a town called Bel-Air."\nIn this fast-forward TV world, would they still listen?