It all begins and ends with Tull

Paleontologists and anthropologists speak of the disputed "missing link," the species that will one day definitively link the human race to primates. In much the same way, rockologists speak of another missing link, the progenitor that definitively married early rock 'n roll with the heavy metal sound, a style that has since evolved without interruption.

Some point to Black Sabbath. A few say Led Zeppelin. Still others call our attention to Jimi Hendrix or obscure bands of that era.

These people are all wrong.

Some of my readers may recall the common wisdom that assailed Jethro Tull's clinching of a late-'80s Grammy for heavy metal act of the year. And while we can all probably agree that Tull's late-'80s work was anything but heavy metal, it's tough to listen to certain tracks on 1971's Aqualung and disagree that Tull's sound that year may very well be the most compelling missing link connecting earlier rock to the frenetic rapid-fire, staccato peculiar to modern-day heavy metal.