Last week's commemoration of the 30th anniversary of Elvis Presley's death has been mapped out for years. But Lisa Marie Presley's idea for how to best mark the date bloomed just three weeks ago.

"People have been asking me to do another duet with him forever, but I had to do my own thing before I went back there," says Presley, 39, whose 20th anniversary duet with her father, "Don't Cry Daddy," was never available commercially.

"So I was ready. I just had to figure out what would be right. And suddenly it came to me, all at the eleventh hour."

Presley's only child used the magic of digital technology to perform the duet with her dad — this time "In the Ghetto," a tale of inner-city blues and redemption.

The younger Presley has added her own touch to this father-daughter reunion: Proceeds from sales of the song, which will be available on iTunes, will benefit a soon-to-be-established New Orleans branch of Presley Place, a transitional housing facility for homeless families. It's a gesture that her benefit concert-focused dad would appreciate.

"I do think this idea would mean a lot to him," Presley says. "Singing this particular duet with him was more emotional for me than anything I'd done before. I wanted to focus on something important, and not just do something silly."

The video shoot, in New Orleans, was simple and quick. "It's just me against a black backdrop, shot in black and white," she says, and uses an unaltered 1969 Elvis recording as its musical foundation.