This is a hybrid Super Audio CD playable on both regular and Super Audio CD players.

"We have here more of the early 1970s quadraphonic recordings made by Philips but which had remained in their tape boxes untouched for 30 years or more because of the realization that none of the quad LP formats of the time was really a viable means of releasing these excellent surround sound recordings to the general public. Since they started in l970 by this time the Philips engineers had perfected their micing to achieve the utmost realism and naturalness in discrete four-channel recording."

--John Sunier, Audiophile Audition