Any examination of Udo Dirkschneider’s metal heart would have to conclude that it’s as healthy as it was a quarter of a century ago, when he started his titanic post-Accept project U.D.O. Pumping furiously, even after all these years, it is the engine that still drives U.D.O., and when the band that bears his name storms the capitol of Bulgaria on the occasion of this concert recording, it seems as if it could explode from his barrel chest at any second – not that such a calamity would silence the indestructible Udo, still one of the most electrifying frontmen metal has ever seen or heard.

Unwilling to concede the upper hand to his former band, even with the roll Wolf Hoffmann and the boys have been on of late, releasing not one, but two nearly flawless, riff-heavy mazes of old-school metal, U.D.O. stakes its claim as Germany’s most potent power-metal force with a relentless, devastatingly heavy double CD/DVD live package, titled Live in Sofia, that celebrates the band’s 25th anniversary. Initiating the launch sequence of a massive U.D.O. reissue campaign slated for 2013, Live in Sofia is a visceral, thrilling document, enlivened by a roaring crowd lending its full-throated support to what is an absolutely ferocious performance from U.D.O. Intense and breathtaking from the first note, Live in Sofia only adds to the fiery mythology of Udo, the well-chosen, 23-track playlist working as a survey of the veteran singer’s long and storied career, its choice of songs running the gamut of Accept classics and U.D.O.’s most flammable material.

Muscles clenched and veins popping, as he seethes with rage and emits spine-tingling screams and animalistic growls, Udo means business every time he opens his mouth, spearheading this invasion of overwhelming sonic weaponry. Setting the attack-dog riffs of lid-lifter “Rev-Raptor” on an audience eager to riot, U.D.O. then rolls into an inferno of guitars in “Dominator,” which dies out just before the shark-like thrashing of “Thunderball” begins and the snarling, sinister menace of the slow-burning “Leatherhead” grows hot – Udo prowling through the thrilling mob violence of each track like a hungry predator. And amazingly, we’re only four songs in, with such adrenaline-fueled action as the rampaging “Break the Rules” and “Two Faced Woman” – both of them boasting tight, clawing hooks – still to come.

A warrior for traditional metal, dressed in his familiar military fatigues, Udo tips his cap to Accept’s glory days by whipping his renegade charges through grinding, writhing versions of “Metal Heart” and 11:10 of the ubiquitous rock-and-roll monolith “Balls to the Wall” – this after sharpening their knives in “Screaming for a Love – Bite,” a prickly nugget of pop-metal poison ivy. Udo can’t escape his past, but then again, why would he want to? As with U.D.O.’s “Vendetta” and “Man and Machine,” the surging dynamics and crushing power chords of Accept’s “Princess of the Dawn,” co-opted at Sofia by a tighter-than-leather U.D.O., testify to the rugged, fierce instrumental prowess of both bands. On the other hand, the darkly melodic “I Give as Good I Get,” the dramatic sweep of “The Bogeyman” and Stefan Kaufmann’s unexpectedly atmospheric electrical storm “Kokopelli” – basically, 11:27 of guitar soloing – speak to U.D.O.’s versatile musicianship. Passion and precision are U.D.O.’s calling cards, and Live in Sofia is the kind of controlled burn that U.D.O. excels at.

There’s nothing excessive about Live in Sofia. Trimmed of fat, parts are played with calculating brutality, and yet is it fair to call U.D.O. regimented? Maybe that’s the right word after all, although there seems to be a mandate for the pack of rabid dogs known as Kaufmann, Igor Gianola (guitar), Fitty Wienhold (bass) and Francesco Jovino (drums) to make their own statements as vociferously as they can, even while working up a frothing lather as a lean, mean unit. Udo would accept nothing less.

Label: AFM Records (CD/DVD box set can be purchased here)