The Indigo Girls are one of those acts who hasn't been near a hits chart or played on radio in years but possess a truly devoted fan base.

Many in last night's virtual sell-out crowd of about 1,500 have been waiting since February, when the duo canceled at the last minute because of illness, to see Amy Ray and Emily Saliers. So it was no surprise that the opening "Pendulum Swinger" was greeted with a rapturous response that didn't subside for the close to two-hour show at The National.

Indigo Girls fans don't merely know the choruses to the pair's songs. They know the verses. The keys. The chord changes. Which songs Saliers plays electric banjo on and when Ray steps in for a melodic vocal exchange.

It's actually quite endearing to watch the devotion being thrown at the singers, because they also appeared to appreciate it.

"Well, we know you can sing," Saliers said with a smile after the crowd sang along to "Fill it Up Again."

What's always impressive about the Indigo Girls -- who sounded pitch-perfect all show -- is that despite the stripped approach of their concerts, their mellifluous harmonizing and well-crafted folk-pop songs are enough to leave even casual fans satisfied. Imagine that -- pure singing can be enough to entertain.

Separately, Ray -- the brunette with the bangs -- and Saliers -- the more honey-voiced blonde -- are respectable singers. But when they hit those harmonies, it's the sound of ethereal beauty.

"Power of Two" remains one of the most tender love songs in recent years -- and sweetly soared last night. It's also an example of how the two can effortlessly stretch beyond their folk roots, which were also on display with "Three Hits," a rustic tune accented by accordion played by Julie Wolf, who also provided keyboards for much of the show.

Ray and Saliers also performed a couple of tunes from a new album that won't be released until winter.

"Driver Education," a Ray composition, would sound great on record if accented by strings, while "Fleet of Hope," which they played for the first time ever last night, fits comfortably in their canon, thanks to Saliers' soft touch.

Fans were likely more than gratified with sturdy versions of "Get Out the Map," their still-beloved "Closer to Fine" and "Shame On You," their last major chart appearance . . . from 1997.

As if this crowd is keeping track.
Contact Melissa Ruggieri at (804) 649-6120 or mruggieri@timesdispatch.com.