Timed to coincide with the annual Earth Day, the event took place in Heap's Essex garden in front of 80 specially invited guests, plus an audience of half a million who enjoyed a live relay via Facebook and the artist's web site.
The central part of the show was a 'silent gig', which featured the assembled guests wearing Sennheiser UK RS 120 headsets to hear the performance.
Following the company's involvement with the December Sessions at London's O2, which included a 'silent gig' by The Feeling, the latter's front of house engineer Jon Sword recommended Sennheiser to Kumar Kamalagharan of Fruit Pie, the production company for the 22 April event.
Kumar - also Imogen Heap's tour and production manager - brought in Falkirk-based Silentgig to supply the audio infrastructure. Silentgig also worked on the December Sessions event and, as the company name implies, probably has more experience of 'silent gigs' than any other company.
"Kumar had plenty of obstacles to overcome on the event, which was to be powered by batteries charged by a combination of a bio-diesel generator, solar panels and 15 riders peddling fixed bicycles," says Silentgig director Chris McCarron. "The aim was to draw no power at all from the national grid, so the main focus for us was to ensure that we drew as little power as possible.
"Parallel with this was reducing the environmental noise to almost zero. We aimed to achieve maximum audio quality, but in a non-intrusive way."
A meeting between Chris, Kumar, Imogen and her manager Mark Woods decided that regular FOH engineer Mike Benson would mix the performance, with monitoring done via Heap's Sennheiser G3 IEM system. The live audience was provided with Sennheiser RS 120 wireless headsets, complete with solar-charged batteries, which would receive the audio via a customised transmitter module with a boosted output.
As well as the 15 cyclists providing pedal power, a further eight would combine with dedicated 'torch wavers' to light the show.
"The cyclists, torch wavers, camera operators and production crew wore Sennheiser RS 110 wireless headsets, using the same batteries as the RS 120s, with the audio feed sent out on a separate G3 IEM system which included the director microphone to co-ordinate the production and power requirements," Chris continues.
"The show was mixed via a Dante Network card, which handled all the inputs and outputs for microphones, VT feeds, broadcast and 'The Gloves' - Imogen's unique, high tech system that involves sensors, synths and microphones to allow her to perform un-tethered to the usual array of keyboards and laptops, using her movements to shape the sounds."
"In terms of the sound, we did everything as we normally would," adds Kumar. "The change was primarily in our mental approach - we opted wherever possible for low-power equipment, we were very diligent in only using power when it was necessary and turning things off when they weren't needed.
"The biggest issue was making sure that we had enough power at any given time. It was mainly a case of keeping the solar batteries topped up for the monitoring, headsets and comms. We achieved this by having a huge array of solar panels in the field that generated a significant amount of power, despite dreadful weather."
Running a bio diesel generator for 10 hours - burning 100 litres of recycled chip fat - overnight before the show satisfied the rest of the power requirements and everyone involved was very pleased at the event's unqualified success.
"The benefits of 'silent' delivery are really highlighted by an event that has this type of environmental ethos," says McCar
