Another of the popular trios of the time was The Limeliters. And like The Chad Mitchell Trio, their lead singer Glenn Yarbrough left the group for a solo career -- and then later reunited with them, though not as extensively as Mitchell did.
Yarborough's solo career wasn't overly successful, though he did have one big hit, "Baby, the Rain Must Fall," which was the title song from a Steve McQueen.movie. He also sang another title song, which I've always liked, but which is largely lost to history, and is the point here.
The team of Arthur Rankin and Jules Bass had a very successful career producing animated TV specials, most notably Rudolph the Red-Nosed Reindeer and Frosty the Snowman. In fact, they did a whole series of popular animated Christmas specials, mostly stop-motion, including The Little Drummer Boy and Santa Claus is Comin' to Town.
In 1977, the did a full-length animated movie for television, long before Peter Jackson got into the picture, with their version of J.R.R. Tolkien's The Hobbit. It has a very good voice cast, including John Huston, Cyril Ritchard, Hans Conreid, Orson Bean, Otto Preminger, Richard Boone and Brother Theodore. And a charming opening-credit song, "The Greatest Adventure, sung by Glenn Yarbrough. The music is by Maury Laws with lyrics by Jules Bass. (Interestingly, the credits say that the lyrics are "written & adapted by...", so I would imagine that the foundation of the words are from Tolkien himself.
(Fun Fact; You'll see in the credits that the script for this version of The Hobbit was written by Romeo Muller. He wrote many, if not most of the Rankin/Bass specials, including their classic, Rudolph the Red-Nosed Reindeer.)
Here 'tis --