Anyone walking by Lutheran Church of the Good Shepherd during a Sunday morning service will hear a sound that is approximately 300 years old.

That is how long mechanically-operated pipe organs have been around, and Good Shepherd, on Fourth Avenue and 74th Street, had one of them installed at last month.

Called "mechanical" because each key is a lever attached to a piston which physically pushes air through the pipe to create the sound, the type of organ at Good Shepherd is increasingly rare. Mechanical organs have largely been replaced by electronic organs.

"The difference between a mechanical pipe organ and an electronic organ is like the difference between a live orchestra and a recording," said Good Shepherd musical director and organist Pedro D' Aquino. "With a mechanical organ the sound is very live, very present -present on the air itself. The best an electronic instrument can do is imitate that sound.

"With this instrument the music of the 17th and 18th centuries can be heard the way it was meant to sound," D'Aquino said.

The organ, with more than 1,200 pipes, took about a year for the Vermont-based Russell and Company to build, and it took four workers from the company eight days —15-hour days—to install it.

Quality does not come cheaply: the church raised $250,000 to pay for the new organ.

Good Shepherd, founded in 1906, originally had a pipe organ of this type. Over the years, as it fell into disrepair, it became too expensive to maintain and was replaced by electronic instruments.

The company that built the Good Shepherd organ, Russell and Company, began as an organ repair service, providing replacement parts for existing organs. But increasingly, churches were in positions similar to Good Shepherd: the old organs were becoming "too far gone" to repair or had long ago been trashed.

Good Shepherd's is the 28th organ to be built by Russell and Company. The organ was dedicated and blessed by Good Shepherd's pastor Reverend Richard Pankow during a ceremony on May 29. Will Headlee, a guest musician, played the organ in the first recital, given later that same day.