As one of rock’s most legendary guitarists, the creator of the ominous riff for the song “Black Sabbath” — not to mention the soundscape of the ubiquitous chant-along “Iron Man” and many dozens of other iconic Sabbath songs, Tony Iommi is one easygoing, unassuming bloke. His melodic sense has even led some to term Sabbath “The Dark Beatles.” Iommi, 73, has been a constant throughout Sabbath’s eight singers, a definite aural architect of the Sabbath’s sound over 50 years. Black Sabbath enjoyed several discrete eras: the Ozzy Osbourne years began in 1968. The first of two time periods with Ronnie James Dio at the helm started in 1980, then came round again under the Heaven & Hell moniker in 2006. (The name is taken from Dio’s first LP with his Sabbath brethren.) Recently, Black Sabbath r...