Believe it or not, this instrumental classic was written for a TV show.... by a comedy writer. The Smothers Brothers Comedy Hour was the show, and Mason Williams was the head writer. Williams wanted the song to be fuel for the classical guitar, so he titled his piece "Classical Gasoline". It was abbreviated on the call sheet as "Classical Gas", and that's the title that stuck.
The Smothers Brothers were interested in launching new musicians on their show, and so they gave Mason a chance to perform his song... which he did in 1968. The song ended up being a massive hit, reaching #2 on the Billboard Hot 100. It also earned Williams a couple of Grammys - the song won three total.
He's backed on vinyl by famed session musicians The Wrecking Crew, and on the show by the Smothers Brothers Orchestra - I think it was an orchestra? - and it's still so dense and layered and beautiful today.