London Records conducted a wildly lavish experiment Saturday night that may set a new cost record for rock advertising campaigns.

To introduce the new album by the Moody Blues (their first in six years), London sponsored a nationally syndicated 60-minute radio simulcast at 9 p.m. (EDT) on over 400 FM stations; it was the record's first play for fans and the press, and was paid for entirely by the record company.With unprecedented secrecy, no advance copies were given to critics or record company personnel, nor were radio program directors permitted to preview the show - all to prevent it from being "leaked" before Saturday, when special tape copies were sent to the cities carrying the show and subsequently hand-delivered to the stations by special courier.

London Records' employes were reluctant to reveal the cost of the promotion. However, according to Katie Valk, press representative for the Moody Blues, it "is probably the highest price ever spent for the single play of an album." Industry sources estimate the cost for the single one-hour program at a minimum of $150,000, and possibly as much as $200,000.

Was it worth it? Bob Hamilton, coproducer of the radio simulcast and publisher of California-based "Fred" magazine, said Friday night that "the promotion will touch an estimated 90 million people. Based upon past statistics and our computer projections, we've determined that we can add an additional 1 1/2 million units to sales. And when you talk about that kind of profit potential, nothing else matters."

Initially, London installed WATS lines at key points across the country to take orders for the show. After hiring personnel to answer the phones, they purchased space in various record trade magazines: teasers leading to full-page ads (even a billboard in Los Angeles) announcing the availability of the program. Once the markets were established, London Records bought radio time: 10- and 30-second spots designed to "hype" the listeners.

But in the case of the Moody Blues album, "Octave" (London, PS 708) - the focus of all this expensive excitement - the hype will have to be a humdinger in order to warrant much response. John Sebastian, programming director for KHJ Radio in Los Angeles, one of the country's taste-makers, said after the broadcast that "the album was artistically bland and the response exemplified that. Several callers complained that the record and the simulcast was a ripoff, that the Moody Blues just got together to make some fast money."

In the late 1960s, the Moody Blues were a rock powerhouse, one of the first such acts to be dubbed "superstars." Their unique blend of soft-rock orchestration with simpering poetic imagery captured the hearts of teen-agers and the imagination of budding musicians. They are generally credited with being the first group to integrate rock'n'roll progressions and symphonic accompaniment into a kind of shaggy-haired magnum opus.

After 1972, though, the Moody Blues quit recording together. Eight years of writing, rehearsing and traveling together - of competing egos and identity crises - had produced a creative claustrophobia that usually results in a group's disbanding. Instead, the Moody Blues decided on an indefinite period of separation.

"Octave," the outcome of those six years apart, is an uninspired echo of our forgetable past. The Moody Blues have not aged gracefully. The 10 songs are completely out of touch with modern sentiments, lacking the spirit or musical energy necessary to communicate with today's teen-agers. Nor are the lyrics exciting: Cliches are heaped upon one another with embarrassing alacrity until the work is smothered. Unfortunatley, there is not one aspect of the album which bears a second hearing.

London Records - an American arm of the British Decca Record group - would do well to minimize their losses, but that appears impossible at this time. According to Ann Adams, the company's publicist, the followup campaign has already begun. In addition to the customary full-page newspaper and magazine ads London is committed to the manufacturer of special four-color posters, window streamers bearing the group's logo, mobiles for in-store display, press kits, neon signs to be given away in contests, pollution stickers (so-called because they contribute to environmental decay) and, in New York City alone, a plastering of over 84,000 outdoor posters. One industry expert estimates the cost of this second phase of the campaign at a minimum of $350,000. And Adams admits that it is "astronomical - simply-beyond anyone's belief."

John Sebastian concedes that because many people may want the first Moody Blues album in six years to add to their record collections, the record could sell well. "But," he said, "as a programmer, I'm worried about finding anything on the album worth playing after this special broadcast. The show may well have sounded a very loud death knell for this album."