Back on the AB III tour fans were suitably perplexed (by perspex, funnily enough) that there seemed to be varying amounts of plastic shielding erected between drummer Flip and the rest of the band. The theory at the time from the band's sound techs was that Myles and Mark's microphones were getting too much interference from the kit itself, and so by throwing up some huge walls of plastic, it might help the sound of the performance overall. Whether it did or not is up for debate from fans who saw them at this time, but as for the more recent tours the shields have disappeared again, which we can only assume means the band's levels work just fine anyway. We've certainly never had any complaints!
