Loreena McKennitt will be at the Providence Performing Arts Center Saturday at 8 p.m. in the last concert of her North American tour.

Of all the emotional effects a singer and songwriter can produce, “bewitching” is one of the toughest. It’s a fine line between entrancing and somnolent, but Loreena McKennitt has stayed on the right side of that divide for more than 20 years.

Part of the reason is chops — an easy, natural voice that can reach great heights seemingly effortlessly. Part of it is the mostly organic nature of her instrumentation, particularly in live performance — while words such as “ethereal,” “mystical” and “swirling” often get used to describe her work, there are no synths or fake strings to be found on her latest live CD/DVD, Nights From the Alhambra. And part of it is McKennitt’s dedication to doing her homework, with original songs and some traditionals about the history of the Celts (as well as adaptations of poems by writers such as Yeats and Shakespeare).

Nights From the Alhambra is McKennitt’s second live record, and for her the concert experience is invaluable.

“I’ve recently taken to the analogy of preparing a dinner for people. It’s like going and shopping for the ingredients, which for me is like doing the research, and going back to the kitchen and coming up with some new recipes. And you can sit down by yourself and eat those things, but it’s always much more meaningful when you can share them with people.”

MCKENNITT SAYS that recording at the Alhambra palace in Spain was “a great privilege, when one really thinks about it, and something I could never have managed doing how many years ago. It is a historical monument of some significance.”

And history is something McKennitt knows about. She describes the importance of research in the songwriting process as her “hobby” and likens herself to a travel journalist or amateur historian.

While her first recording came out in 1985, the process began, McKennitt says, in 1990 after a visit to a Venice museum exhibit on the Celts. “I thought, ‘Wouldn’t it be interesting to follow that pan-Celtic history and use it as my creative springboard?’ I found myself adopting that approach, probably akin to many travel writers. You find a theme.”

“I sort of developed this amateur interest in the history of the Celts. So the research involves traveling to these places, reading as many books as I can, speaking with the academics and authorities . . . I gather a lot of information, a lot of images, and start distilling that into a creative document.”

1994’s The Mask and Mirror took its inspiration from Celtic roots in Spain; 1997’s The Book of Secrets was a “musical travel document” from all over the world, and 2006’s The Ancient Muse traces Celtic history back to 500 B.C. and the musical traditions of Eastern Europe.

WHILE MOST ARTISTS pick an album title that exemplifies the themes of the songs therein, McKennitt says that the album title is the first step in the process, and that once the title and theme are established, “the title sits like a knob at the top of an umbrella, which these arms that lead out to the songs reach.”

Even with authoritative heft behind it, McKennitt says, songs such as “Raglan Road,” “The Lady of Shalott” and the hit “The Mummers’ Dance” are a personal take on the history. “It probably relates more to the process of creating a personal impressionistic painting, based on the research.

“The Celts . . . never wrote anything down themselves. What is known is somewhat limited, although there are some fantastic pieces in museums throughout Europe. I’ve been less concerned about approaching things in an academic or authentic way — ‘This is what they did, and this is what it sounded like’ — and more in telling the story of where they went and some of the places and geography and scenes that they would have encountered.”

Growing up in Winnipeg, McKennitt began singing folk and traditional music in the late ’70s, and recorded and sold her first cassette herself in 1985. Celtic music and traditions weren’t as well-known then as they are now, but she says that didn’t deter her.

“I never really thought about it in those terms. I was smitten by the Celtic sound; I wanted to try to work in it as well, or just play it for the love of it. And then in ’85, I said, ‘Well, why don’t I make a cassette?’ Not really having any major plans. And one thing sort of led to the next.”

She used the money her family had set aside for her veterinary education to make Elemental in 1985, and sold it herself, busking when necessary to keep the music in front of people. “There seemed to be enough people interested in it that it encouraged me that it was something that I should pursue.”

IT WASN’T EASY doing it herself, she says — the ’80s were not as friendly to do-it-yourselfers as the Internet age is — but it was an education.

“I didn’t know anything about the business. So it was a real do-it-yourself and learn-as-you-go type of project. In retrospect, I’m very happy that it did happen that way. Even though I’d like to say that I knew what I was doing, I didn’t. But I knew more what I didn’t want to do as various situations presented themselves.” By the time she signed with Warner Music Group in 1991, she had a track record recording her own music and handling her own affairs. “Whatever the future held for me, it would be based on the basis that I would remain independent.” To this day, she finances and releases her own records, using Warner only for distributing and advertising.

MCKENNITT WILL BE wrapping up her North American tour when she hits Providence, and she says she’ll take most of the winter off, doing some writing and researching, and hit the road again next year. She’s mulling a few film projects (her music has been used in several films, perhaps most notably The Mists of Avalon) and a guest-DJ stretch at Sirius satellite radio. “And I have my other life, just putting in the garden and going for runs and such.”

Loreena McKennitt sings at the Providence Performing Arts Center, 220 Weybosset St., Providence, Saturday night at 8. Tickets range from $29.50 to $72.50; call (401) 421-ARTS or online at ppacri.org

rmassimo@projo.com