"Sing a Simple Song" (Sly & The Family Stone)

Before Sylvester Stewart (a.k.a. Sly Stone) slipped into cocaine-fueled paranoia in the 70s, he made the tightest/loosest album of his career: Stand! (1969).  The three albums that precede it have some decent songs, but you can tell Stone was still trying to figure out the right blend of soul and psychedelic rock.  Not to mention the right balance of when to party and when to preach.
But Stand! fires on all cylinders.  There's catchy social commentary (the ubiquitous "Everyday People"), gospel-tinged motivational music ("I Want to Take You Higher"), and a lot of humor (the 13-minute "Sex Machine").
But the best song on the album in my opinion is "Sing a Simple Song."  From Freddie Stone's downright stanky guitar riff to Greg Errico's clockwork drumming (which has been sampled hundreds of times over), it encapsulates the whole Sly & The Family Stone sound in a little under 4:00.  Upbeat yet lowdown, churchy yet earthy, funny yet poignant, "Sing a Simple Song" is about trying to maintain perspective in an increasingly pessimistic, fast-moving world.  The thrifty lyrics also suggest that, when people put aside their problems and get back to basics, harmony is possible.
Although the sentiment borders on flower-power cheesiness, it's counterbalanced by The Family Stone's verse-trading delivery, which is sincere and true.  Plus, there's bassist Larry Graham singing do-re-mi-fa-so-la-ti-do in his deep baritone—a purposely jokey nod to the 1965 movie-musical The Sound of Music.
It's the kind of song that makes you feel good to your core.
It's also the kind of document that makes one wonder if the mad genius of 1971's There's A Riot Goin' On would have sounded radically different had Stone not slipped into addiction.