Madonna’s longtime background singers Niki + Donna are still expressing themselves

As one of Madonna’s longtime background singers and dancers, Niki Harris was pushed right up to the borderline to get into the groove with Donna De Lory before they set out with the Queen of Pop for the first time on 1987 “Who’s That Girl” tour.

“I came in at the very end. I had 17 songs to learn, 17 costumes I had to fit in,” Harris, 61, told The Post. “And I had to learn all the songs in a week because the following week we were gonna be opening in Japan.”

And Harris and De Lory would end up being right by Madonna’s side — and each other’s —through the 1990’s Blond Ambition tour (memorably captured in the groundbreaking  1991 documentary “Truth or Dare”), 1993’s Girlie Show and 2001’s Drowned World Tour.through the 1990’s Blond Ambition tour (memorably captured in the groundbreaking  1991 documentary “Truth or Dare”), 1993’s Girlie Show and 2001’s Drowned World Tour. 

Now, as the duo Niki + Donna, they will once again be in close proximity to the Material Girl when they play the Green Room 42 in Manhattan’s Theater District on Saturday and Sunday — right before Madonna performs at Madison Square Garden on Monday as part of her 40th anniversary Celebration Tour.

“Nikki and I, like, value each other more than ever,” said De Lory,  59. “We’re still working together, and the fans come out, and they love it. We’re nostalgic about that time, and they are too. “

“And we’re so grateful that Madonna put us together, you know?” she added. “I mean, that’s her brilliance. She just knew who to cast, and she knows where the magic is.”

Harris and De Lory rediscovered their magic together after they did a reimagining of the 1993 “Erotica” single “Rain” in 2016.

“We kind of really made it our own,” said De Lory. “We did an acoustic version with live strings and upright bass.”

Then while Harris pursued jazz and De Lory explored new age music, they came together to release the EP “Two Friends” in 2017. 

It’s all part of their journey in harmony that will be celebrated at the Green Room 42.

“The show is really to celebrate and honor our friendship,” said Harris.

“When you’ve gone decades and decades and decades of being with somebody [through] births and deaths and just life experiences that really shift and change people’s lives, you need to look at that person sometimes and go, ‘Thank you for pouring into me.’ ”

It’s a spirit of sisterhood that goes all the back to their glory days supporting Madonna.

“She was like a big sister and a role model for me,” said De Lory.

And the love was justified both ways.

“Nikki and I totally had her back,” said De Lory. “Like, ‘Don’t worry, if you feel like you’re losing your voice, we can sing louder.’ ”