 The Byrds ' third album , Fifth Dimension , was released in July 1966 . Much of the album 's material continued to build on the band 's new psychedelic sound , with McGuinn extending his exploration of jazz and raga styles on tracks such as " I See You " and the Crosby @-@ penned " What 's Happening ? ! ? ! " . The album also saw Hillman coming forward as the band 's third vocalist , in order to fill the hole in the group 's harmonies that Clark 's departure had left . The title track , " 5D ( Fifth Dimension ) " , was released as a single ahead of the album and was , like " Eight Miles High " before it , banned by a number of U.S. radio stations for supposedly featuring lyrics that advocated drug use . In addition , the album 's front cover artwork featured the first appearance of the Byrds ' colorful , psychedelic mosaic logo , variations of which would subsequently appear on a number of the band 's compilation albums , as well as on their 1967 release , Younger Than Yesterday . 
