The Byrds, The Notorious Byrd Brothers (1968)
While earlier songs like "Eight Miles High" and several of David Crosby's contributions were fairly trippy, Notorious was a more deliberately psychedelic, atmospheric album than its predecessors, with great songs as well as a great use of space and sequencing. It kicks off with "Artificial Energy," an upbeat, horn-driven song uncharacteristic of the rest of the album (kinda like "Armenia City in the Sky" leading off the contemporaneously-released The Who Sell Out), before settling into a more typical jangly folk-infused sound, only with more texture and aesthetic weirdness than prior works.
While the album forgoes the Dylan covers that had peppered earlier (and some later) albums, there are a couple ringers in the two Goffin-King-penned tunes, which are also among the best songs on the album -- the beautiful, pastoral "Goin' Back" and the anthemic, timeless "Wasn't Born to Follow" (the latter drafted for use in the Easy Rider film).
Which doesn't mean Roger McGuinn and Chris Hillman (with a few Crosby co-writes) weren't holding their own. "Draft Morning" is a gorgeous, emotionally stark anti-war hymn, interrupted by mid-song gunfire, and probably my favorite Byrds song. "Natural Harmony" is a nice piece of headphone-friendly psychedelia (as is the sonically dynamic "Tribal Gathering"), and "Change Is Now" perfectly bridges the jangly Rickenbacker sound of early singles and the late 60s mind-altered vibe that permeates the album. Throughout, the absence of a few founding members does not seem to have hindered the band's remarkable use of rich harmonies.
Here's an Easy Rider clip with "Wasn't Born to Follow":
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