BY JON FERGUSON

Staff Writer

Amy Ray and Emily Saliers, who together are the Indigo Girls and are performing Thursday night at the Whitaker Center in Harrisburg, liked their new batch of songs so much they decided to record them twice.

Truth be told, it was producer Mitchell Froom's idea, but Ray and Saliers were willing accomplices.

So when the two women went into the studio to record their latest album, "Poseidon and the Bitter Bug," it was with the intention of first recording the songs supported by a full band and then going back and recording them all again, this time as an acoustic duo.

They had three days left of studio time to wrap up the acoustic disc.

"It was more challenging than I thought it would be," says Ray, the dark-haired one. "I didn't expect it to be that hard because that's how we play, mostly. But, actually, it was really hard. It was real hard to get a performance I felt would stand on its own completely naked and without any overdubs and without any fixes. It was good for us, to see that we were still challenged by playing as a duo."

It's not surprising that the Indigo Girls  are still challenging themselves because they have always challenged their audience.

The duo, which released its first album in 1987, has been remarkably consistent, making intelligent, impassioned music that always sounds like they're going for broke.

That was certainly true of the hit single "Closer to Fine," which helped win them national attention and a Grammy more than 20 years ago, and the same can be said for most of the songs on "Poseidon."

The Indigo Girls never sound like they're going through the motions because there is nothing half-hearted about their music.

Ray — whose songs tend to have a harder, more rock-oriented edge than those of Saliers, whose tunes are rooted in folk — says they were energized, not enraged, when the Indigo Girls were dropped by Hollywood Records.

The duo, instead of looking for another major label to sign with, decided to go the independent route, which is quickly becoming the path of choice for most musicians these days.

"It was a total opportunity and a chance to reinvent sort of what we do and how we approach it on a business level, which, for me, is a lot of fun," Ray says. "When the business is kind of a drag and you feel like the label is not on your side, it kind of gets demoralizing at some point. It's hard to just focus on what you do and feel positive about it."

Fans have already benefited from the Indigo Girls' independence as it's unlikely a major would have gone along with their plan to include the two different versions of "Poseidon" when it was released earlier this year.

"It made the art have more energy as well, I think," Ray says of their departure from Hollywood.

As well as performing with Saliers, Ray also maintains a solo career. Her most recent solo album is "Didn't It Feel Kinder."

Ray is quick to point out, however, that her solo career revolves around her recording and playing live with a rock band.

She has, on occasion, performed all by her lonesome.

"I didn't like it," she says. "I like to have my friends with me. I like to have someone up there playing with me. I think it's because I'm so used to playing with Emily, Since I was 15, that's what I've done."

The Indigo Girls

Thurs. 7:30 p.m. $35, $45

Sunoco Performance Theater

Whitaker Center, 222 Market St.

Harrisburg, 214-ARTS
www.whitakercenter.org