On March 4, when Napster started blocking access to music protected by copyrights to comply with a federal court order, its competitors hankered to fill the gap.

One of the companies that has tried to make inroads into Napster's enormous population of users is Aimster, a company that helps users share music via America Online's Instant Messenger software. Aimster, based in Albany, also tapped into the hard drives of users of Napster directories and came up with a novel solution to Napster's blocking: the Pig Encoder (www.aimster .com/pigencoder.phtml).

Reasoning that Napster's blocking system is based on the names of artists and the titles of their songs, the system is simplicity itself. It changes each word in the file by taking the first letter of each word and placing it at the end of the word. The result, pig Latin without the added ''-ay'' syllable, turns the word ''music'' into ''usicm,'' and hashes ''copyright'' into ''opyrightc.'' So anyone who wants to download the works of Metallica would search for ''etallicaM.''

The program, of course, would be trivially easy to circumvent, if Napster simply added a list of similarly scrambled words to its blocking list. A Napster spokeswoman refused to comment.