Looking for an interesting way to spend a springtime Saturday? Try transforming yourself into a musical instrument - a "sacred harp," no less - by participating in a day-long celebration of traditional American folk hymnody.

On Saturday, April 26, shape-note singing aficionados from western New York, Pennsylvania, Ohio, and Canada will gather at the Rochester Mennonite Meetinghouse specifically for the unbuttoned pleasure of singing, literally at the very top of their voices, for an entire day. SUNY Brockport English professor Thom Metzger, amateur musician, occasional City Newspaper contributor, and local organizer of the event, emphasizes that this "this is not a concert, not a performance, per se, but instead a participatory musical event. Listeners are always welcome, but the tradition of shape-note singing is inclusive. People of all experience levels are welcome to drop in and join us."

But, what is "shape-note" singing? And what, exactly, is a "sacred harp," and why would you want to be one?

The designation "shape-note" comes from the style of notation used in this music. Instead of the uniformly round noteheads we all encountered in grade school music classes, shape-note singing employs different notehead shapes, each one helping the singer find the right pitch. Think of it this way: as Maria von Trapp, a young and athletic Julie Andrews needed boats, bikes, and a full staircase in Salzburg's Mirabelle Garden to teach the von Trapp children the "do-re-mi-fa-sol-la-ti-do" functional steps of the octave scale. But shape-note singing boils it all down to four simple functions, embedded within the note-shapes: "fa" is triangular, "sol" is round, "la" is square, and "mi" is diamond-shaped. It's that easy - and no aerobic activity required.

The term "sacred harp" was originally the title of a 19th-century collection of simple, sacred part-songs belonging to a tradition dating back to the American Revolution. But more specifically, a "sacred harp" is the human voice itself, the means by which this remarkable repertoire is realized into an exuberant outpouring of sound and feeling. According to Lisa Grayson, author of "A Beginner's Guide to Shape-Note Singing," "In Sacred Harp singing, loud is usually good, and louder is better. This is partly because of the music's origins as a true folk music sung by ordinary people for pleasure and worship, and partly because loud singing provides more catharsis, more instant gratification, than controlled singing does."

Grayson notes that for some early church leaders, the intense physical pleasure of singing loudly raised questions about the potential sinfulness of this repertoire, despite the overtly pious texts. "It can get fairly raucous," agrees Metzger, "and we are unashamed of the volume. It's a bit raw, too, unfettered by notions of good taste and musical decorum."

The purely sensory attractions of shape-note singing seem to have overpowered the genre's traditional spiritual associations, and obliterated all conventional ideas of proper performance perimeters, as well. While some devotees still regard the singings as a religious observance, for the majority, Grayson notes, "Sacred Harp singing is primarily a community and social event. No particular religious belief or affiliation is expected or required."

As for performance practice, there are no auditions, no rehearsals, no separate seats for an audience (the singers are the audience), no applause after each tune, and no official conductor. The singers divide into parts along something like conventional soprano-alto-tenor-bass voice ranges, and stand in a square configuration. The song leader changes for each tune, giving any singer who wishes the chance to choose a tune, stand in the center of the square to keep the beat, and experience the full force of the glorious noise washing over him or her.

Metzger notes that a local group of Sacred Harp singers has been around for about 15 years, including "everyone from absolute beginners to professional musicians." Sacred Harp singers, he says, "tend to be doers, rather than passive recipients of entertainment. Many are contra dancers, or players of folk instruments."

Metzger himself discovered the music by accident, but was immediately captured by the "soaring harmonies and ear-ringing volume of these white spirituals with gnarled old-word roots. Plugging into the elemental force of the music, I felt a passion like no other I've found among musicians. Raw and visceral, this music is not an imitation of black gospel, or slick Nashville country. It's real ‘roots' music, brash and uncompromising, and a boisterous ‘no' to much of modern high-tech culture."

So-shape-note singing isn't high art, isn't popular entertainment, and isn't officially religious. The why do so many people love it? Lisa Grayson explains: "For us, the singing is an end in itself. We sing for the pure joy of it."