Ronnie James Dio’s first album with Black Sabbath gets everything right from beginning to end. The Iommi / Butler / Ward sound is less doomy than the Ozzy era but no less melodic. Ronnie's voice projects more than Ozzy ever could; that opened up new avenues for Sabs to venture down. Lyrically it’s more Dio than Sabs but I fail to see that as a criticism. It’s produced by master knob-twiddler Martin Birch, who finds the perfect pitch and balance to give everyone equal footing. Albums rarely achieve such perfection. A genuine classic.