Legendary keyboardist Jon Lord, best known for his work with Deep Purple from the 1968 to 2002, died July 17 after a battle with pancreatic cancer. Dream Theater keyboardist Jordan Rudess posted the following tribute on Twitter: "I'm very sad to hear about the passing of Jon Lord. He was an inspiration to me!...Tonight's Dream Theater in Boston was dedicated to the spirit of Jon Lord. I improvised a piano piece which I directed to his memory."

Opeth frontman Mikael Åkerfeldt had even more to say, as Deep Purple have been a huge influence on the band. Not only did they cover Purple's "Soldier of Fortune" as a bonus track on the special edition of Ghost Reveries, but their 2010 live CD/DVD set, In Live Concert at the Royal Albert Hall, came in cover art that was a tribute to Deep Purple's 1970 album Concerto for Group and Orchestra.

Here's what Mikael had to say:

"We're very saddened to hear about the passing of the great Jon Lord. Our condolences go out to his family and friends. He's obviously partly responsible for Opeth ever being formed, so we're in massive debt to him.

"Martin Mendez and Martin Axenrot obviously had the pleasure of working with, and playing with Lord, and both said it was such an amazing experience. He was a sheer musical genius. Axenrot even said that when he'd asked what bpm (beats per minute) a song was supposed to be in. Lord had said, 'Around 140 bpm,' and started clapping his hands in the desired beat. Axenrotchecked with his metronome and sure enough, Lord was clapping in exactly 140 bpm!

"Jon Lord. We love you. Your music lives on and your memory will never fade."

Watch the video of Opeth's bassist and drummer playing with Jon Lord in two parts, above and below, now.