I dunno, I always thought it was kind of annoying. But when Kate Smith graced the Flyers with her semi-operatic vibrato on a version of "God Bless America" on December 11th, 1969, before a game against the Toronto Maple Leafs, a tradition was borne, in perhaps the most tradition-fixated sport of the four majors. The Flyers won the game 6-3, and from then on, whenever the Flyers needed a boost in karma, they called on Big Red--either live or on tape--to come do her thing.
The returns, at least initially, were somewhat staggering. The first three years after Kate Smith first supported the Orange and Black, the Flyers were 19-1-1 when her "God Bless America" was played before a home game, and just 31-38-28 when she did not. Such stock was eventually placed in the power of Kate Smith to swing a big game that before game six of the '74 finals, Bruins stars Bobby Orr and Phil Esposito tried a reverse jinx by sending her flowers and shaking her hand. (It didn't work).
Smith's anthem has continued to be played (admirably sparingly) before big games, and over the course of the last 40 years, Flyers are a still fairly stellar 77-21-4 in such games. After her death in 1986, a statue of her was erected outside of the Spectrum.