It's best to remember this about Post-Apocalypto: it's not a proper Tenacious D album but rather a soundtrack to the group's animated Internet series.
Jack Black first mused about an Internet series to Marc Maron way back in 2012, but it took six years to reach fruition, by which time Black and Kyle Gass were pushing their fifties and sixties, respectively -- an ideal time to make the leap from film to animation.
Post-Apocalypto, which made its debut in September 2018, makes sense as an animated project but less so as an album.
Running 21 tracks, most hovering around a minute long, Post-Apocalypto is a scattershot collection of sketches, jokes, and song fragments, all telling a story that is reliant on visuals.
Some of this can work in isolation -- the band's loving mockery of classic rock retains potency; there are some throwaway laughs -- but this is the first Tenacious D record that plays as a comedy album, not a musical one.
That would be fine, but the problem is that Post-Apocalypto often sounds like a recorded version of the audio portion of the animated series, which just raises the question: why listen to this when it's easier -- and funnier -- to watch the series?.