This is the Intro of Shine on you crazy diamond but using the Gilmour Sound-On-Sound effect. Basically it is an effect for simulating the long keyboard chords as a background with out keyboards. First used in Meltdown Live 2001/2002 (acoustic event), he strums with volume down, then smoothly raises the volume up. This way, there is no attack on the note, it’s all just smooth sustain. There are two effect lines, line A for solo and line B for Sound-On-Sound effects, it consists of a Roland SDD-3000 Digital Delay set at 1500ms with long feedback. The trick is the expression pedal placed between the two lines (usually after the input compressor) which functions as an A/B switch. I tested it using CV plugin with Rise and fall control but it doesn't work... or better it works but uncontrollable in real situation. You must use an external expression pedal (midi or future Mod one). In my case I've used a normal exp pedal connected to Cholocate midi footswitch Experiment an modify if you like!!!