Pink Floyd is a perfect example of one of the original Prog Rock Bands. People tend to think of Prog rock as virtuosos and complex music, but Prog came out of the Psychedelic era, and the earliest Prog rock bands, which included Pink Floyd, the original Genesis, Jefferson Airplane, Moody Blues, Yes, and so many more, were known for their Symphonic Rock focus. "Piper at the Gates of Dawn" is a semi-pop album, but after they lost Syd Barrett, "A Saucerful of Secrets" is a 100% Prog album. From there, they developed their own sound. Live at Pompeii is one of the greatest Prog performances of the early 70s. They ooze creativity and thinking outside the box. Watching that show, you see the greatness that would be DSotM just permeating their performance.
Let's put it this way: I think that everyone can agree that "Xanadu" by Rush is a paragon of Prog. Floyd had a different mindset to making music, but the long song format, the creative washes, the symphonic elements, and the focus on the instrumental were all in the same vein. And it is definitely no stretch at all to think that Floyd influenced the later, hard-core Prog band's thinking about "painting with sound".
Let's put it this way: I think that everyone can agree that "Xanadu" by Rush is a paragon of Prog. Floyd had a different mindset to making music, but the long song format, the creative washes, the symphonic elements, and the focus on the instrumental were all in the same vein. And it is definitely no stretch at all to think that Floyd influenced the later, hard-core Prog band's thinking about "painting with sound".