was the lead guitarist and, along with Roger Waters
, lead vocalist for the progressive rock group Pink Floyd
. Gilmour joined Pink Floyd in 1968, when he was asked to replace former front man and guitarist Syd Barrett
. Barrett was becoming increasingly difficult to work with (due to his deteriorating mental state), so Gilmour stepped in to fill the void. Gilmour's contributions helped to define what would become known as the "Pink Floyd" sound.