Dio Singing Backing Vocals

Many knows that the late Ronnie James Dio did backing vocals (or featured) on a number of tracks. He can be heard on Ian Gillan's 40 years anniversary album, Gillan Inn, singing "Day Late and Dollar Short".
The other time was with Queensryche, when he Leant vocals as  Dr.X on the Operation Mindcrime II album.
But it was a big surprise when came to my knowledge that the legendary musician did backing vocals on the song "Give Me Kindness", from David Coverdale's second solo album, Northwinds.
More interesting is that Ronnie's wife (and later his manager), Windy, is singing backing vocals on that song too.
I would love to hear the full story of how all his come around! During that time Dio was part of the first reincarnation of Richie Blackmore's Rainbow.
By the way, Northwinds is a great album, more blues than rock. Some critics considers the music from that album is the early trademark to Whitesnake MKI sound we all used to listen to in the years that followed.