Not the least fascinating thing about Black Sabbath is that there have been no fewer than three very different bands in its history, conveniently separated by the singers who shaped them: Ozzy Osbourne, Ronnie James Dio and Tony Martin. (And one can even add Sabbath No. 4 and Sabbath No. 5, for one experimental album each, since "The Seventh Star" with Glenn Hughes and "Born Again" with Ian Gillan, both from the mid-1980s, neither of which has anything to do with the other three "eras".) I confess that the Martin-era is my least favourite one, but this may well be because I came to these albums after I had been quite familiar with everything recorded with Ozzy and Dio during the 1970s and early 1980s. However, personal taste is a poor excuse to neglect the years with Tony Martin. After all the man recorded five studio albums with the band and they all range from good to very good, with occasional sparks of greatness: