FREEPORT — Rod Regier has direct perspective on this country’s growing interest in early music. He builds fortepianos and harpsichords similar to the instruments that Mozart, Haydn and Beethoven used when they composed in the late 1700s and early 1800s.

They’re much smaller than contemporary pianos, with less range and a fuller sound.

It was, and still is, a niche market. Lately, though, Regier has found that market expanding.

Instead of making pianos for players who specialize in early music, he and workshop assistant Kris Carr are building for conservatories that have added early-music performance to their curriculum and for piano players who are incorporating early instruments into their performance repertoire. In recent years, he’s built early-music pianos for The Juilliard School, Yale School of Music and other leading conservatories. Last week, the South African pianist Kristian Bezuidenhout sat down at one of Regier’s Maine-built fortepianos at Alice Tully Hall at Lincoln Center in New York, to perform music by Schubert.

“Early music is not on the fringe anymore,” said Regier, whose shop is in Freeport. “Early instruments are becoming part of the norm.”

Early music is considered any piece of music composed in the Renaissance, Baroque and early Classical periods. For years, musicians performed that music on contemporary instruments. In the last generation or two, many musicians have performed on instruments built during the time when the music was composed or, more commonly, on contemporary instruments constructed in the manner of those that were common in 17th and 18th centuries. Their goal is to get as close as possible to the sounds the composers had at their disposal when they wrote their music.

This weekend, Portland audiences get a chance to hear what that music sounds like. The Portland Conservatory of Music hosts the Portland Early Music Festival, with three days of music at Woodfords Congregational Church, beginning Friday. The festival is in its fourth year and includes music written in the 17th and 18th centuries by English, Italian and German composers.

“Symphonies from Berlin to Timbuktu are paying attention to their performance practices and incorporating early-music instruments,” said founder Timothy Burris, who plays the lute and teaches at the conservatory as well as at Colby College in Waterville. “The tonal quality is just remarkably different.”

For musicians and connoisseurs, the appeal is authenticity. When we hear Mozart played on piano, we hear a facsimile of what Mozart intended, Burris said.

Because of their shape and size, and some of the materials that are used, early instruments sounds different than their contemporary counterparts. They offer a different palate of sounds.

For instance, the viola d’amore looks like a violin, but plays very differently. The violin has four strings. The viola d’amore has either six or seven strings, as well as “sympathetic” strings just below the strings that are bowed. The sympathetic strings vibrate when the other strings are bowed, creating a more robust sound.

Early in his life, Beethoven, who was born in 1770, composed on a five-octave, 63-note fortepiano. Later in life, in the early 19th century, he would have composed on a fortepiano with 61/2 octaves and 80 notes. Today’s piano has 88 notes and seven octaves.

Similarly, early music played on the guitar sounds different than when it’s played on the lute. “I’m not saying it’s better, but it has characteristics you just can’t duplicate with the guitar. The guitar ends up being a worthy imitation in a lot of cases, but it’s not the piece that the composer envisioned,” Burris said.

RAFFAEL SCHECK, a cellist from Waterville, will perform for the upcoming festival in Portland. His grandfather was Gustav Scheck, who founded a conservatory in post-World War II Germany. Gustav Scheck was a pioneer in the early-music movement and trained many of the European musicians who advanced the movement in the 1970s and 1980s.

Scheck teaches history at Colby and plays music on the side. He uses a German cello built in the second half of 19th century. He plays on steel strings with a convex bow, which bends away from the strings as opposed to a modern bow, which bends toward the strings. The bow is similar to the style that players in the 1800s would have used, but the strings are not. “I should be using gut strings, which were used at the time of baroque music. But my cello will respond well to steel strings, with a warm and soft tone,” he said. “In some sense, I am cheating.”

American classical musicians began paying closer attention to early music a generation or more ago. It developed as a specialized niche, with centers in Boston, New York and elsewhere. Now, more audiences are hearing it. In 2011, the Portland Symphony Orchestra hired several early-music specialists to perform “The Passion of St. John” by Bach, for example.

That was about the same time Burris began the Portland Early Music Festival. It’s still finding traction. Audiences generally are small but loyal.

CHARLES KAUFMAN of Portland, founder and director of the Longfellow Chorus, began playing baroque bassoon in the late 1980s. He was playing modern bassoon and freelancing around New England while teaching. Through church, he met someone who played an early recorder.

That sparked his interest in discovering more about early bassoons. He acquired one through a former student and mastered it. He now owns several early-music bassoons, all modern reproductions made by a German craftsman.

Playing an early instrument is difficult, he said, because a musician has less to work with. There are fewer notes, and some instruments are less responsive. Modern instruments are clean and perfect. Early-music instruments can be clunky. “Part of the beauty of early music is the imperfection of it,” Kaufman said. “Early-music musicians overcome the imperfections of these instruments by giving them character. We give these instruments personality.”

They also tend to play at a faster tempo. “That enlivens the music,” he said. “It solves the problem of the instruments not sounding perfect. The performance will have so much character, it becomes something different and gives you a sense of what it sounded like originally.”

BRUCE FITHIAN was active in the Boston early-music scene and singing across the globe when he took a job teaching voice at the University of Southern Maine in 1985. He tried to start an early-music ensemble when he arrived here but found nobody to perform with. “There were no singers or players, so I just gave up,” he said.

By 2000, that changed. He met Burris and others, and in 2008 he began the St. Mary Schola, an early-music ensemble devoted to master works from the Medieval, Renaissance and Baroque periods.

Composed of singers and accompanying instrumentalists, the ensemble performs elegant chamber music across the region and is based at the Episcopal Church of Saint Mary the Virgin in Falmouth. The stone chapel and its excellent acoustics reminded Fithian of the old churches where he sang when he lived and studied in France.

The ensemble performs a trio of concert programs most years, at the church in Falmouth, the Cathedral of St. Luke in Portland and elsewhere. “What we have found is that when people do come, they have a very different experience than when they hear music in a big concert hall,” Fithian said. “They realize this is magical.”

THE QUEST for that magic has helped elevate Regier, the Freeport piano maker. He began making pianos in the late 1960s and started his business in 1973. He moved to Maine in 1979.

Regier, 65, is one of those Maine craftsman who is known better outside of his state than within. From his shop in Freeport, he ships fortepianos all over the country, and also repairs and restores others. His latest, which he will deliver this month, is going to a pianist in Springfield, Illinois. He put the final touch on this week, affixing his signature plate to the instrument.

His instruments sell for between $40,000 and $60,000. He works in a well-lit barn that’s attached to his house on South Street. There are no signs announcing his business or other markings to indicate his trade.

He got a degree in civil engineering from Massachusetts Institute of Technology and was working as an oceanographer at Johns Hopkins University in Maryland when he decided to follow his instinct and begin making pianos.

An “enthusiastic amateur player” who is married to a harpsichordist, Regier always loved music and woodworking. Making pianos combined those two loves and held more appeal than studying oceanography.

He appreciates seeing early music become more accepted, although he’s not necessarily benefiting from it. He and his assistant are a two-person shop. They’ve been busy for years already.

“We’ve made a lot of instruments here, and we’re going to keep making them,” he said.