There's a bevy of "I'm not in right nows" replaying themselves endlessly for exasperated ears. The Electronic Industries of America estimates that 7 percent of Nielsen households (88 million homes) use answering machines. The association projects that 4,400,000 additional answering machines will be sold to retailers from factories this year, for an estimated sales figure of about $334 million.

While conventional logic would assume a plethora of witty prerecorded tapes to ease a caller's tension and frustration at the machine, most attempts to break into the prebeep market have failed. Only Phonies, a company with centers in New Jersey, Tennessee and Florida, seems to be successful. It also appears to be one of only a few such companies in operation.

"There may be some other companies out there, but I'm not aware of them," says Lloyd Burkley, 46, , who formed Phonies with partners Anderson Humphreys, 38, and Martin Segal, 46, eight years ago. "There certainly isn't another company that has the distribution we have."

Eastern Onion, of singing telegram fame, temporarily marketed "Fun on Hold" tapes a few years ago, where humorous voices entertained (or infuriated) callers put on hold. But, according to Eastern Onion manager Mickey Orlov, 42, production costs to record and edit the tape were too high and "by the time we got it done, it got to be too expensive and people just didn't want to buy it."

Another problem for humor tapes, says Telephone Warehouse of Georgetown owner Carl Berger, 32 (who has seen humorous tape enterprises "come and go"), is "it tends to get old very fast. Just how often do you want Richard Nixon to answer your phone?"

Burkley attributes the company's success to the quality of its tapes, which feature a variety of messages, from straightforward statements to the Rich Little imitations that Phonies introduced three years ago. A call to the New Jersey office has Little's "Humphrey Bogart" telling you to leave a message, 'because if you don't, you'll regret it. Maybe not today, maybe not tomorrow . . .' "

Keeping a variety of tapes is another way to stay afloat, says Burkley, whose company also does business in Australia, Canada and Europe. Phonies, he says, has an arsenal of 180 different voices (15 available tapes with 12 voices on each), and he estimates he will have sold more than 100,000 cassettes this year.

The Rich Little imitations are the most popular tapes, says Burkley. And incidentally, the most requested character is Richard Nixon.

For a catalogue of tapes from Phonies: Phonies Inc., P.O. Box 2110, Cherry Hill, N.J. 08003.