Black Sabbath, Download Festival, Castle Donington Sparks, Bush Hall, London

After some Download downpours the sun came out for a doddery Ozzy and (most of) his band. Cue doom-metal riffs of unmatchable heaviosity

The British summer can be such a disappointment, can't it? Not the mud and the rain, but the lack thereof. I can't imagine anything more fitting, on hearing the reunited Black Sabbath bludgeon slowly through the eponymous opener of their eponymous debut album, than standing in a sludgy Midlands field and hearing Mother Nature replace the sound effects on the record with real-life drizzle and thunder.

By the final day, Download – presumably so named because it invariably pours down loads – has dried up, allowing a jokey "And on the Sabbath day, Ozzy said 'Let There Be Sun'" caption on the big screens. Nevertheless, metal fans – never more than a hair's breadth away from primitivism – have regressed by the time I arrive. The first thing I see is a man with his penis out, urinating on his friends, who are rolling around on the floor laughing.

Everything this festival crowd is into, for better or worse, was invented by Black Sabbath between 1970 and 1977, so they're the ultimate closing act. Ozzy Osbourne's sidekicks, Geezer Butler and Tony Iommi, may look like retired musketeers. But the latter, his plastic-coated fingertips (originals lost in an industrial accident) roaming frets marked out with big gothic crosses, can still deliver doom-rock riffs of unmatchable heaviosity: "War Pigs", "Sweet Leaf", "Iron Man" and, above all, "Paranoid".

Ozzy himself is a doddery figure, repeatedly shouting "I can't fucking hear you!" in the same voice he uses to inform Sharon that one of her Pomeranians has crapped on the carpet. But no one could deliver the line "My name is Lucifer, please take my hand" in such a convincing wail.

The only shame is that the reunion is a partial one. "Where the fuck is Bill Ward?" demands a heckler as Ozzy hails some competent young random behind the kit. Where indeed. The genial, strawberry-nosed drummer is absent, claiming he was presented with an "unsignable" contract (a claim refuted by the Sabbath camp). A sad situation, but this is what happens when you don't pay your Bills.

"It feels like being naked," says Russell Mael at the launch of Sparks' Two Hands, One Mouth tour, "so we appreciate your pretending like we're not naked." For the first time in their four-decade history, the Mael brothers are playing a whole show with no backing band, and it's a charming, engaging way to present an underrated body of work. The intention, the singer explains while indicating his elder brother, Ron, is to "show off his lyrics". And rightly so. Most bands, if they'd written even one line like "A rainbow forms, but we're both colour blind", would retire.

If Sparks have been too clever for their own commercial interest, pioneering and discarding new genres (dark cabaret, operatic rock, electro pop), then their hardcore fans only love them for it even more.

Sporting a bit of an emo fringe and smart airline pilot's blazer, Russell stands like a boxer, leading not with a fist but with his left eyebrow, getting ready to whomp that sucker with wit rather than aggression.

Ron Mael, the cult figure within this reluctant cult band, receives deafening chants of "Ron! Ron! Ron!". The unsettlingly impassive pianist responds by getting up for a comical speed-skater dance, while his younger sibling quizzically eyes the synthesisers.

Highlights of a magnificent set include the baroque "Under the Table with Her", the heartbreakingly self-aware "When Do I Get to Sing 'My Way'?" and, from the days when Sparks were bona-fide pin-ups, "This Town Ain't Big Enough for Both of Us". In any sane universe, Sparks are big. It's pop that got small.

Critic's choice

The Isle of Wight Festival dominates the weekend, headlined by Primal Scream, Tom Petty and the Heartbreakers, Pearl Jam and Bruce Springsteen, and with The Darkness, Madness and Lana Del Rey among the best of the rest at Seaclose Park, IoW (Thu-Sun). Meanwhile, BBC Radio 1's Big Weekend brings such stars as Jay-Z, Kasabian, Plan B and Rihanna to London's Hackney Marshes (Sat, Sun).