''By order of the Majority for Musical Morality, this album contains secret backward messages,'' reads the sticker on the cover of the new Styx album, ''Kilroy Was Here'' (A&M SP-3734). Photos on the back and the inner sleeve of the album are taken from a 10-minute movie featuring members of the group. The film is an integral part of the Chicago-based rock quintet's new show, which comes to City Center for four nights, starting March 31.
In the film, James Young, Styx's 33-year-old lead guitarist, plays Dr. Everett Righteous, a demagogue who turns his own cable network into a potent political base. Blaming society's ills on rock music, Dr. Righteous and his organization, the Majority for Musical Morality (MMM) gain enough power to have rock music banned in America. Any similarities between the MMM and the Moral Majority are not purely coincidental.
''Kilroy Was Here'' is the brainchild of Dennis DeYoung, Styx's 36-year-old senior member, keyboardist, lead singer, and writer of most of the group's hits. Mr. DeYoung plays Robert Kilroy, a famous rock star who is falsely accused of murdering a protester at an MMM rally and sent to prison. Tommy Shaw, Styx's other guitarist, plays Jonathan Chance, the underground leader who contacts Kilroy and helps him escape. Chuck and John Panozzo, the twin brothers who make up Styx's rhythm section, play characters named Lieut. Vanish and Col. Hyde.
Although the comic book scenario for ''Kilroy Was Here'' seems farfetched and simplistic, it contains a kernel of seriousness. In the last two years, Styx has been targeted by fundamentalist religious groups for the ''backward masking'' of satanic messages on its albums. Backward masking means the recording of subliminally perceived messages that can only be deciphered when a record is played backward. At the height of the Beatles' psychedelic period, the rumor of Paul McCartney's death was fueled by the message, supposedly backwardly coded on the sound collage, ''Revolution No. 9,'' ''Turn me on, dead man.'' Since then, many other groups have played with the notion of coding cryptic backward messages that the devoted listener could then detect by rotating a disk backward by hand.
The idea that such messages might be sinister has gained currency only in recent years, with the rise of fundamentalist Christian fringe groups. Far-fetched as their crusade against rock seems, it has nevertheless gained enough credence to inspire local legislation. On Feb. 3, 1983, the Arkansas State Senate passed a bill, by 86 to 0, requiring that all records containing backward masking be labeled as such by the manufacturer. Cited in the legislation were albums by the Beatles, Pink Floyd, Electric Light Orchestra, Queen, and Styx.
The Majority for Musical Morality sticker on the cover of ''Kilroy Was Here'' is Styx's response to the charges of satanism. And on one cut, the James Young song ''Heavy Metal Poisoning,'' Styx has indeed backward masked a cryptic-sounding Latin message, ''annuit coeptis novus ordo seclorum,'' which happens to be the inscription on the Great Seal of the United States.
The attack on Styx is rife with ironies, since the group is wellknown for its socially benign stance. The group is politically centrist and has contributed money and support for the development of solar energy. Their songs unabashedly uphold the traditional Protestant virtues of hard work, social responsibility and monogamy. Audiences at Styx concerts are more wholesome looking than the audiences for any other big-name arena rock group. The song that earned Styx its place on the fundamentalist blacklist was James Young's anti-cocaine song, ''Snowblind,'' in which the words, ''Oh satan, move in our voices,'' were supposedly backward masked. Mr. Young denies that any message was coded into the song.
The fact that the issue of backward masking could engender any legislation at all suggests that rock music, which so many people are pronouncing dead these days, still has the power to inspire fear, loathing, and ecstasy. Indeed the power of good arena rock groups like Styx, Foreigner, and AC/DC, whose audiences are 95 percent teen-age, has been consistently underestimated by the rock press. Styx's records, in particular, have been routinely dismissed by rock critics for their simplistic upbeat lyrics and diluted blend of pop, hard-rock and art-rock. But while the records do indeed sound like timid pastiches of Three Dog Night, Yes, and the Who, the same music that comes off sounding stiff on record expands to anthemic proportions in the concert hall. It's a matter of dynamics, and few groups wield them with more skill than Styx.