The dedication of a new pipe organ is cause for celebration. Here is an instrument that can approximate the sound of an orchestra in full thrall or whisper out a melody that is barely audible. The organ may give joy, reflect sorrow, invite us to sing along with it or prompt an extended solo meditation. It belongs to the public as no other instrument.

And now Washington's oldest house of worship, St. Paul's Episcopal Church on the grounds of Rock Creek Cemetery, has a beautiful new instrument created by the esteemed Dobson Pipe Organ Builders Ltd. of Lake City, Iowa. The $500,000 organ was played in public for the first time on Sunday afternoon, when the church's music director, Graham Elliott, and the Rev. Martin L. Smith led an Evensong in the small, immaculately restored chapel, portions of which date to 1775.

John Panning, from the Dobson company, was in charge of installing the organ and was in attendance Sunday; in organ-world parlance, he is known as the "tonal director." In a statement, he listed several necessities of a good organ: "It must produce gracious sounds congruent with the human instrument. It must be capable of great dynamic flexibility, so that it can support everything from a single voice to an entire assembly. It must make the greatest possible effort to accommodate the centuries of music for worship. It must encourage and inspire artistic minds, so that new songs of the church may be created in our day."

A gigantic cathedral organ would be out of place in the intimate confines of St. Paul's. And so Panning envisioned a "true romantic instrument" that "thinks like a large organ even though it is relatively small."

That he had succeeded was apparent from the first notes of the afternoon concert, which included music by Frederick T. Atkinson, Sir Percy Buck, Herbert Howells and Elliott himself, as well as an a cappella choral rendition of Benjamin Britten's "Hymn to St. Cecilia," the patron saint of music. The sound is balanced, blended, varied and nuanced, and it was deftly shaped by Elliott's sure and imaginative musicianship. In the grand tradition of church organists everywhere, he saved his loudest and most assertive playing for the last verse of the final hymn, when he pulled out all the stops and made a joyful noise indeed.

Evensong is, in effect, a musical service in which the priest and the chorus mostly take over the call and response more usually shared by the entire congregation. Elliott calls it "a meditative act of worship" rather than an active one; indeed, it had many of the qualities of a chamber concert. The nine-voice Choir of St. Paul's added much to the afternoon with the eerie, piercing purity of its singing -- from darkest bass notes to radiant, stratospheric highs. The lush, slithering harmonies of the Britten hymn have rarely sounded so fresh.

This was the opening concert of a weeklong festival at Rock Creek, which will continue through Saturday, and include concerts of jazz, baroque music and sacred works by one of Washington's most celebrated homegrown composers, Duke Ellington. Daily 7:30 p.m. concerts are $20, $10 for senior citizens and students. Lunchtime performances and other events are free. Call 202-726-2080 or go to the church's Web site at www.rockcreekparish.org. The setting, at Rock Creek Church and Webster streets NW, couldn't be much more lovely and historic; what passes for the "real world" in the summer of 2004 seems ever so far away.

The new, $500,000 pipe organ at St. Paul's Episcopal Church in Washington, which was played in public for the first time at a service Sunday afternoon.