Mamma Mia, here they go again: Pop superstars ABBA� have returned to the stage after an absence of more than 40 years. But this time around, the band is using a power pack combo of bleeding-edge tech and innovative venue design to create a whole new kind of hybrid concert experience. Designed to bridge the gap between the physical and virtual realms, it features avatars of the Swedish group singing and dancing alongside a 10-piece live band in a purpose-built stadium in London. The six-year, US$175 million project was a masterclass in not just harnessing new tech but in collaboration. George Lucas’ visual effects company Industrial Light & Magic brought 850 team members across four studios together to animate the hyper-realistic avatars using hundreds of cameras and four body doubles in motion-capture suits. Project leaders even modernized the band’s iconic outfits, dressing the so-called ABBAtars in designs by Dolce & Gabbana� and Erevos Aether�. But that was only half the challenge...