Yes, one of the most successful progressive-rock bands in rock 'n' roll history, has canceled its 26-city 40th anniversary tour, which had included a concert Aug. 15 at WaMu Theater at Qwest Field Events Center.

The reason: health concerns.

Frontman and co-founder Jon Anderson was admitted to a hospital last month after suffering a severe asthma attack and has since been diagnosed with acute respiratory failure and told by doctors to take it easy for at least six months.

"In the wake of my recent respiratory attack," Anderson said in a statement, "doctors have advised me to spend the coming months resting and recovering.

"I'd like everyone to know how deeply disappointed I am by this turn of events. I was looking forward to celebrating our music with the amazing family of Yes fans once again."

The tour was set to kick off July 12 in Quebec City, Canada. There are no current plans to reschedule the trek.

Earlier this year, Yes had conducted an online search to find talented, aspiring rock musicians to join them on tour.

In addition to Anderson, band members include Chris Squire, Steve Howe, Oliver Wakeman and drummer Alan White, who lives in the Seattle area.

White recently performed an impromptu set at Canlis restaurant with Jimi Hendrix impersonator Randy Hansen and guitarist Don Wilson of The Ventures, who had just been inducted into the Rock and Roll Hall of Fame.

Ticket refunds are available at place of purchase.