Doro Pesch joined KISS bassist/vocalist Gene Simmons on stage during his concert yesterday (Sunday, July 15) at Masters Of Rock festival in Vizovice, Czech Republic to perform the KISS classic "War Machine". Fan-filmed video footage of her appearance can be seen below.

Gene executive-produced Doro's second solo album, 1990's "Doro". She later said in an interview that the experience of working with Simmons "was a dream come true. Gene always showed me when you start a new record you start from zero again," she said. 'I was always a big fan of him and became a big fan of the person after working with him. So intelligent. I love that! It's was so great to watch him working with all the musicians. He was a great motivator, fantastic! Every time before I went into the studio, I was driving my car like maybe 20 minutes and I was very happy. Right before I went into the studio, my knees were shaking. 'Not again!' [Laughs] He made me very happy in so many ways. He really tried his best. I remember one song the mix wasn't coming out right. I was totally bummed out. I was really nervous. Gene said, 'Just go to your room and wait there.' I was in L.A. At 9 o'clock in the morning, the receptionist called me and said there was a gentleman here and left the tape for you. I couldn't believe it was nine o'clock, and I said, 'Okay.' I listened to it and Gene makes the call. It was the song 'Mirage' and it was so good. It moved me to tears when I wrote it. It came out so good. He definitely made sure the mix was perfect. He was there for us in so many ways. I think he was the best producer we ever had."

Doro's new album, "Forever Warriors, Forever United", will be released on August 17 via Nuclear Blast.

The long-awaited follow-up to 2012's "Raise Your Fist" will be the German singer's first release since 2016's "Love's Gone To Hell" single.

Last year, Pesch celebrated the 30th anniversary of WARLOCK's "Triumph And Agony" album by performing the LP in its entirety at select shows around the globe.