Spanning over a half-century of prog-rock mutations, the King Crimson discography is a rabbit hole with no end. Even a castaway track like the psycho-jazzy 1970 B-side “Groon” packs more ideas into three minutes than most bands muster across a whole album. But what’s most impressive about King Crimson is how they only seem to grow more potent with age: check “Happy With What You Have to Be Happy With”, a 2003-era crusher fit for a 21st-century schizoid man.