It's Favourite Album Friday (which is feeling like it ought to be renamed Deep Purple Friday) #3. Today I shall be mostly listening to Deep Purple in Rock (1970).
I defy anyone to argue against this being one of the key albums in the development of hard rock, probably only equalled by Black Sabbath's and Led Zepellin's debuts for impact and influence on the genre. Whole books have been written about this single album (it's true, I've got one of them!)
It also contains what I personally consider to be the best rock song of all time (and the greatest piece of music ever written by anyone whose name was not "Bach"). This is literally the song that made me a rock fan: