A knife’s edge is a dangerous place to tread, but the members of the New York-based Irish rock band Black 47 have been navigating one for 20 years.

Since he founded the group in 1990, singer/songwriter Larry Kirwan has used humor and eclectic instrumentation to achieve a blackly irreverent tone that tempers the message of songs about serious social and political issues.

The trick is in the blood, said Kirwan, a native of Wexford, Ireland.

“In the Irish experience ... there aren’t too many victories in its long history,” he said, laughing. “It’s one defeat after another. The only way to deal with that was with a black humor.

“To us, with humor, you can get a message more palatable, and it might stick better.” Tonight, Black 47 will see what sticks at Miller Plaza as this week’s Nightfall headliner.

The band’s name comes from 1847, one of the bleakest years of the Irish potato famine. Despite that somber origin, however, Black 47 is well known for songs such as “Maria’s Wedding” and “Green Suede Shoes,” which are as jubilant as its 2008 album “Iraq” is critical and contemplative.

Black 47 shows range just as widely. Despite the band’s odd juxtapositions in the set list, however, the audience has never seemed bothered, Kirwan said.

“The sheer amount of ingredients in the mix, no one seems to question it,” he said. “It doesn’t seem jarring. I don’t know why that is.”

For the last 20 years, Black 47 has upheld an organic philosophy regarding its evolution, Kirwan said. With a lineup of five musicians with improv backgrounds playing everything from saxophones to uilleann pipes, the band has been free to incorporate elements from everything from reggae to jazz in its music.

“Nothing seemed that off-limits to us,” Kirwan said. “The odd thing is that it all seemed to fit.

“That’s the thing that’s surprised me, that it seems to have its inner core, that you can try anything and it will work to some degree.”