that's untrue, sorry. Sure, some pre-recorded effects have always been part & parcel with a live Floyd show - the heartbeats, radios, airplane sounds, pig grunts, etc. Often, drummer Nick Mason would play to a "click track" - a metronome-like device in his ear, so that the band could stay in synch with the films being projected and effects unfolding around them. If that's what you mean then yes, they always employed pre-recorded material into their shows (well at least from DSOTM on). But vocally, with Waters and Gilmour sharing duties, they sang their lines live. And that's the big difference here.