It feels so good to believe in the myth of Rick Rubin — the idea that there is a beardy guru living on some Malibu mountaintop, radiating wisdom and positive vibes strong enough to make your songs turn out as awesome as the first Danzig album.

The legendary record producer launched his career in the ’80s at Def Jam Recordings where he helped introduce New York hip-hop to the rest of the planet. But Rubin’s myth didn’t take shape until he squeezed fresh pathos out of the Red Hot Chili Peppers with 1991’s “Blood Sugar Sex Magik.” (“Funky Monks,” a short and terrific documentary about the recording session offers a glimpse into Rubin’s mellow superpowers.)

In the years that followed, Rubin gained a rep for helping a slew of artists access their innermost greatness. He convinced Johnny Cash to cover Nine Inch Nails. He guided the Dixie Chicks through a redefining career pivot. And just last year, he helped Kanye West pull his latest maniac opus into focus. He’s still a sage capable of helping any artist — regardless of generation or genre — surface their deepest, truest self.

So what happened on this new Jennifer Nettles album?

After years of making garish country hits as the lead singer of Sugarland, Nettles is taking a solo turn with “That Girl,” out this week. As usual, the employ of Rubin signals the desire to be taken as a Serious Artist, but aside from some lyrical quirks that probably would have been snuffed out on Music Row (“I’ll even tolerate your skanky fake hair,” she sings on “Jealousy”), it’s difficult to detect Rubin’s touch. Nettles has a gigantic voice that she tends to overuse, but here, she keeps it (somewhat) in check. Perhaps Rubin – a guy whose methods favor verbal guidance over soundboard knob-spinning — simply said, “Shhh.”

Either way, “That Girl” is a shoulder-shrugger. And it’s no fluke. Here’s a sampling of other blech Rubin has produced in recent years:

– “Born Free,” Kid Rock’s 2010 mash note to Bob Seger.

– Josh Groban’s “Illuminations.”

– Linkin Park’s last two albums, “A Thousand Suns” and “Living Things.”

– Last year’s brittle Black Sabbath quasi-reunion album, “13.”

But for every handful of clunkers, there’s a “21,” that chart-dominating, multi-platinum, partially-Rubin-produced 2011 juggernaut from Adele. Blockbusters like these keep the myth of Rubin’s infallibility intact. But his various whiffs reinforce the other half of the myth: he’s real, which is to say, human.