No, it's not a flock of sheep, it's today's riff. The band is Crowbar (the Canadian band Crowbar, that is), and this is probably their most well known song. It comes from the 1971 album Bad Manors (a name also later given to their Greatest Hits album).

The chord progression/riff here is only a measure or two long, but you can play your way through the whole song with it. The partial F chord at the end of each measure is sometimes played once, and sometimes twice. There's no particular pattern to when to play it once or twice, so just wing it, and mix both ways in there, as you please.

CROWBAR - "Oh What A Feeling"      (K.Jay Fordham/R.Greenway)

https://www.angelfire.com/planet/zerofret/annesblog/canriffs.txt

I couldn't find a full version of the song on YouTube or MySpace, but there's an audio clip of it on this page. It has a bit of the Intro and part of the first Chorus:

http://www.amazon.com/Bad-Manors-Golden-Hits-Vol/dp/B000001CWO