The simplest machines are the most versatile and adaptable. And when it comes to ’70s guitar-rock, things don’t get much simpler than AC/DC and KISS. Most of their classics have just a few moving parts: A chunky riff, a four-on-the-floor drumbeat, a razor-sharp chorus and an air-guitar solo. They’re so basic anybody can learn them. That’s why generations of teenage basement bands got their start covering these cuts. It’s why umpteen artists have released AC/DC and KISS tribute albums and converted their songs into everything from bluegrass and country to punk and orchestral. And it’s why singer-guitarists Eric McFadden and Marceese Trabus can still find new ground to explore on their recent discs. For American journeyman McFadden (whose vast resume includes stints with Eric Burdon, George Clinton and plenty more), the unplugged approach displays far more inspiration than the title of his album Eric McFadden Does AC/DC: Acoustic Tribute. Lowering the lights as well as the volume, the virtuoso player and gruff vocalists strips a dozen headbanger anthems down to their building blocks, then remakes them into blues, jazz and folk numbers with the help of a subtle backing band. Some tracks (like Beatin’ Around the Bush or Whole Lotta Rosie) are played fairly straight; others (like Girls Got Rhythm, Have a Drink On Me and You Shook Me All Night Long) are retooled without irony into dusty late-night ballads. But everything retains enough of its DNA to be instantly identifiable. The same cannot always be said for German KISS fanatic Trabus’s Hotter Than Hell. On his fifth (yes, fifth!) full-length celebration of the onetime Hottest Band in the Land, Trabus also takes the deconstructionist approach to chestnuts like Parasite, Let Me Go, Rock ’n’ Roll and the title cut. But his one-man-band conversions tend to run looser, weirder and woollier — Got to Choose becomes strummy folk-rock, Goin’ Blind is recast as a tender lament and Mainline is exploded into a 10-minute psychedelic noise-rock freakout. Even weirder: Between his crisp guitar work, freewheeling approach and Americanized vocals, Trabus often sounds like like KISS and more like Jack White fooling around in his home studio. So if you want real versatility, you’ll find it here. But ultimately, either one of these discs should have enough reverence and reinvention to get the job done with fans. Simple as that.