Yes

Yes released the album Tormato in 1978, right after the success of Going for the One (1977), which saw the return of Rick Wakeman on the keyboards. This would be the final album with Anderson, Howe, Squire, and Wakeman playing together. The album suffered a bit from the musical climate of the day as punk music began to congeal in Britain. Progressive rock was becoming an old horse; people were tiring of endless, lofty instrumentation and over-your-head lyricism, both classic trademarks of Yes's early days, and prog rock in general. The songs on Tormato are much shorter and radio friendly, and despite landing on the top 10, the album was reviled amongst the formerly dedicated Yes audience and hardcore prog fans alike. With the less-than-stellar public reception, Jon Anderson (lead singer, lyricist, and composer) took the opportunity to bow out, with Wakeman quickly following suit. Still, the album does have plenty of classic Yes moments, namely the closing track (posted earlier) "On the Silent Wings of Freedom," which could stand right alongside the most raucous and inspired moments of Fragile (1971).
"Madrigal":

and the chart-topping "Don't Kill the Whale":

Birth Control

it's been a while since i've posted some prog. here's Birth Control live with "Skateboard Sue" from their 8th studio album, Increase (1977). That's Zeus B. Held on the keys, there.

Todd Rundgren

Todd Rundgren with "Intro" and "Breathless" from his 1972 album, Something/Anything?:

Alan Parsons

From his solo album, On Air (1996):
"Cloudbreak"

King Crimson

classic prog, "Larks' Tongues in Aspic" part I circa 1973

This Heat

recorded for John Peel in '77.

Popol Vuh

"Kyrie" from Hosianna Mantra (1972)

Jimmy Hotz

seen here showcasing his crazy synthesizer (which he invented):

"Vision Ships" from Beyond the Crystal Sea, recorded and produced by Jimmy:

YES

the answer for every question.
closing track from the oft-overlooked 1978 album Tormato (1978).

Amon Düül II

Amon Düül II grew out of an improvisational music collective that had been known simply as Amon Düül, a musical counterpart to a larger communal society in Germany. As Amon Düül became somewhat more cohesive, the name change to Amon Düül II happened in 1969 and more albums were recorded. Many members of the group flowed in and out of circulation and played with other bands as well.
"Between the Eyes" from the Rattlesnakeplumcake / Between the Eyes 7" single (1970)

Tangerine Dream

spanning 5 decades, Tangerine Dream is one of the most influential electronic groups out there. Alongside others like Kraftwerk, they catapulted the popularity of krautrock outside of Germany into the stratosphere in the late 60's and 70's. They continued on (with a few lineup changes) into the 80's and 90's experimenting with what became known as "New Age" music, and they're still out there today touring every once and a while. "Kiew Mission" from the 1981 album Exit:

Guru Guru

forming in '68, Guru Guru went on to record 20 albums and jammed around with some of Krautrock's finest performers like Can and Amon Düül. "Electric Junk" from Hinten (1971):

Frank Zappa & The Mothers of Invention

zappa and the mothers, live studio session for the BBC, 1968. ignore the repetition of the opening bit...: