Yesterday I read an interview with Plant and Krauss in The Telegraph (UK). I copied it - its not long. Here's a bit -
Krauss grew up in Champaign, Illinois playing fiddle and singing just such songs. On a Zoom call from Nashville, she gets suddenly tearful recalling the lifechanging impact of seeing sibling bluegrass artists Jim & Jessie, the Osborn Brothers and the Del McCoury Band at a County Fair in 1979. “It’s singing so close you can’t tell one voice from another. It makes me emotional just talking about it, it’s so sweet,” she says. “It is precision singing. As a lead rock vocalist, Robert is so much the opposite of that. The ranges of our voices land in different places, and the fact that it doesn’t blend is what makes the blend. It creates a third voice.”
"It’s like being at night school,” says Plant. “I’m still learning the different flexing of harmonic options. You can hear me fitting in almost like some sort of vocal jigsaw puzzle.”
When I ask if this is difficult for him, he says “Oh yeah, it’s hellish! It’s a whole different mindset,” says Krauss. “It creates quite a feeling to hear him in that harmony role, because the identity of his lead singing is so powerful. It’s a voice that’s been part of everyone’s musical experience for decades.” When Plant and Krauss toured together during 2008, they performed Led Zeppelin’s Battle of Evermore, with Krauss singing Sandy Denny’s parts (the sublimely talented Fairport Convention singer who died in tragic circumstances at the age of 31 in 1978). “I’d look over, and there’s Robert, and I just got chills.”