The key figure was missing from this diverse double bill. Not Massive Attack, who had invited Bristol torch singer Martina Topley Bird and Deptford eccentrics The Shortwave Set to share a bill at their Meltdown Festival. I was half expecting Brian "Danger Mouse" Burton, the man who has done such a fine job of producing both acts' new albums.

Anglophile New Yorker Burton, who could have had his pick of the A List after huge successes with Gorillaz and Gnarls Barkley, followed his passions rather than cash when choosing the projects that would make up an insanely busy 2008.

He was virtually the only person who bought and loved The Shortwave Set's last album, and Topley Bird's debut solo release from 2003 wasn't much more popular, despite a Mercury nomination. Now, thanks to a psychedelic production touch that has brought much colour and sharpness to their current releases, both are strong contenders again for next month's Mercury shortlist.

Topley Bird appeared first, looking supremely bored initially, her woozy, languid voice apparently capable of sending even its owner to sleep. Gradually she grew bolder - a smile here, a jokey tapdance there - and by the time she had picked up an electric guitar for squalling closer Too Tough To Die, she had earned her warm applause.

She was best when avoiding the slow-motion trip hop sound that first made her name as Tricky's muse 13 years ago. Both Carnies and Baby Blue had catchiness and bounce to spare, and when she went a cappella with her four backing singers, as on a soulful cover of The Maytals' Sweet And Dandy, she was mesmerising.

My entire row had left before The Shortwave Set appeared but they missed some charming, distinctly English indie pop with a twist, thanks to the retro samples of David Farrell. Andrew Pettitt and Ulrika Bjorsne shared vocals while the rich sound swelled around them on tracks such as Replica and Glitches 'N' Bugs. The vintage machinery and white boiler suits made for a sonic laboratory well worth visiting. Hopefully the fame of their new producer will lead a lot more people to pop in.