Regardless of one's religious persuasion, Cecilia is a saint worth getting to know. Indeed, her posthumous career is one of the most interesting in all of hagiography.

It seems she was a real person. Some sources say she lived in the first quarter of the third century A.D., in Rome, in the Trastevere district where the 9th-century Basilica of St. Cecilia now stands. Other sources put her in Sicily 50 years or so earlier. In any case, she was the daughter of a wealthy pagan nobleman, and she died - probably while still in her teens - for the sake of her Christian faith.

According to the Acts of St. Cecilia, the 5th-century document that marks the beginning of Cecilia's popularization, her martyrdom was particularly awful. First the pagans chopped the heads off Cecilia's husband and brother-in-law. Then they arrested her and tried to cook her to death in a steam bath from which all the water had been drained. That failing, they called in the ax-man. He gave her three hearty whacks, yet she didn't die, even though her head was dangling by a mere thread of skin. She hung on, so to speak, for a full three days. And only then, after she'd been visited by many of her fellow Christians, did she go to her reward.

Although she had a husband, Cecilia was a virgin. And her connection with music stems from the alleged circumstances of her wedding. She had been promised by her father to an aristocratic young pagan named Valerian. Since she had sworn herself to chastity, she obviously did not want to go through with the marriage and all that it entailed. So at the ceremony, while musical instruments played around her, she prayed that she might remain as pure in body as she was in spirit. Her prayers were answered; later that night, in the nuptial chamber, she converted Valerian to Christianity.

It is a very great distance from Cecilia's wedding to early 18th-century London, where Handel composed a cantata in honor of St. Cecilia's Day. The piece was sung in Italian, but the original text, by Newburgh Hamilton, is in English. It reads, in part:  'Thou, harmonious Cecilia, Who didst ravish with thy singing, Who didst enchant with thy playing, Oh, mayst thou grant to this gathering Of thy worthy followers That they may match thy merits, For a noble birth, lacking virtue, Is made equal with an obscure one." If one takes a literal view of the story as told in the 5th-century Acts, Cecilia ought to be patron saint not of musicians but of persons who find music's charms utterly resistible.

By Handel's time, Cecilia had become not just an appreciator of music but a virtuoso performer. This remarkable transformation of a woman who perhaps had a tin ear into one of the world's legendary virtuosos did not begin until the 15th century. Before that, the patron saints of music were Gregory, David and Job. Gregory was a ''real'' saint, the 6th-century pope credited with originating the style of liturgical singing known as Gregorian chant.  Because they lived in Old Testament times, David and Job were ''pseudo saints.'' Like Gregory the Great, Israel's King David was a musician, a fabled harpist and a composer of psalm tunes as well as texts. As for Job, Chapter 30, Verse 31 of the Book of Job has him saying that ''my harp is turned to mourning, my flute to the sound of weepers.''

Whether their sainthood was real or psuedo, Gregory, David and Job had at least some sort of musical credentials. Until late in the 15th century, Cecilia had none at all. She was revered, but only as a virgin martyr. Her popularity had grown considerably since the writing of the Acts in the 5th century. Her body was exhumed in the year 821 and re-interred with pomp and circumstance in the basilica in Rome that bears her name. Even though her corpse was discovered ''uncorrupted,'' a hundred years later her severed head was on display - simultaneously - in no fewer than five churches. But she was the patron saint of marital chastity, not of music.

Nevertheless, and for reasons that still elude scholars, a cathedral finished in Albi, Italy, in 1480 was decorated with images of St. Cecilia holding - and presumably playing - a portative organ. In 1502, in the Belgian town of Louvain, the magistrates fairly demanded that a newly formed society of musicians name itself not after St. Job but after St. Cecilia. And in 1570, the town of Evreux in France was the site of the first documented St. Cecilia music festival.

Richard Luckett, in a paper delivered in 1972 to the Royal Musical Association in London, offers a credible explanation of Cecilia's rather sudden move into musical circles. The early Renaissance, he notes, was the period in which the craft guild - the forerunner of the labor union - came into being. It was also a time of tremendous growth of cults devoted to the Virgin Mary and a time that brought unprecedented social status to artists and artisans of all sorts. From the leather workers to the blacksmiths to the musicians, every guild needed a patron saint. For musicians, Luckett writes, the obvious choice would have been Mary herself, for it was well-known that her assumption into heaven was accompanied by the singing of a choir of angels. But since the mother of Jesus held such a unique position in the Christian pantheon, for the musicians' guild to take her as their own would have been regarded as outrageous. So they drafted another blessed virgin, Cecilia, and they twisted the legend until she, too, was involved with celestial harmonies. Within a relatively short period of time, Luckett says, St. Cecilia was identified not just as a superb performer on the organ but as the instrument's inventor.

And he offers two theories as to why the 16th-century organ builders did not try to preempt the claim of the musicians' guild. The plausible one is that the organ builders didn't have a guild of their own; they belonged to the guild of cabinetmakers, whose patron had traditionally been St. Luke. The other theory, more interesting but a bit far-fetched, has to do with the fact that in pre-electric times the air that coursed through an organ's pipes had to be pumped by hand. ''Representations of Cecilia's martyrdom often show enthusiastic assistant executioners blowing the fire under her bath with bellows,'' Luckett writes, ''and this I once thought to be the key to the whole mystery. But no solid evidence supports the view, though the bizarre association is not altogether unlikely; Sebastian, after all, was the patron of archers.''

In any case, by the end of the 16th century, Cecilia - performer, composer, inventor, whatever - was well established as the patron saint of musicians. A few years after the concept of a St. Cecilia music festival had its debut in Evreux, a St. Cecilia Society was founded in Paris. In 1579, the composer Palestrina helped found the Academy of St. Cecilia in Rome. By 1585, Cecilian festivals were taking place throughout Italy, Spain, Germany, France and the Netherlands. In 1599 her body, still ''uncorrupted,'' was again exhumed, and this time it served as the model for a marble sculpture by Stefano Maderno.

England did not get on the Cecilian bandwagon until 1683, when Henry Purcell, for a festival in London, was commissioned to compose no fewer than three anthems in her honor. In 1687 the official poet for the St. Cecilia festival in London was John Dryden, and the official composer was not Purcell but an Italian named Giovanni Battista Draghi. Draghi's setting of Dryden's ''Ode to St. Cecilia'' has fallen by the wayside, but the poem has had a distinguished history. It has attracted the attention of many composers, the most famous of whom is Handel, who used it for his 1739 ''Ode for St. Cecilia's Day.''

The Dryden poem (''From harmony, from heav'nly harmony'') is too long to quote here in full. This is just an excerpt:

Those are the last 16 lines, enough to illustrate - one trusts - how potent a musician Cecilia came to be in the millennium and a half after her death.