"Sylvia"

Time for a cliche. Time for a visit to the Natural History Museum, to the dinosaur room. Look! There's the fossilised skeleton of Diplodocus. Huge, lumbering, slow, ponderous. What's that sign say? "Progressive rock musician. Believed to have roamed the surface of the earth in the late 20th century. This specimen has been dated to 1971."
If you ever feel the need to jump into the deep end of prog rock, you could do worse than start here. Focus was a Dutch band made up of some rather talented individuals with jazz and classical training: pretty much the starting point for all prog rock, as it happens. Before the genre became obsessed with classical scope, volume and scale (see Emerson Lake and Palmer), people were trying to cross-match rhythms and styles and see what they could cook up.
"Sylvia" is a triumph of good taste, utterly crammed with what later became cliches; gorgeous great washes of Hammond organ, jittery minor-chord riffs that sound like they could have been culled from later prog-pop epics like "Pinball Wizard", smooth guitar passages that rear up and shout "virtuoso" -- and this in the day before guitarists became stars in their own right -- neo-classical flourishes and vaguely insane operatic background vocals.
It's hard to dislike an innocent, involving and ambitious song like this, despite the self-indulgent bastard child it created. Be kind, be generous to this song, because it really did help to start a whole new sound.