 According to Roger Waters , Barrett came into what was to be their last practice session with a new song he had dubbed " Have You Got It Yet ? " The song seemed simple enough when he first presented it , but it soon became impossibly difficult to learn and they eventually realised that while they were practising it , Barrett kept changing the arrangement . He would then play it again , with the arbitrary changes , and sing " Have you got it yet ? " Eventually they realised they never would , and that they were simply bearing the brunt of Barrett 's idiosyncratic sense of humour . Waters had called it " a real act of mad genius " . 
