It's called timestretching. You basically have to chop up the sound into little bits and play them back in a staggered fashion. The technology has a history fr

It's called timestretching. You basically have to chop up the sound into little bits and play them back in a staggered fashion. The technology has a history from before the digital age: http://www.wendycarlos.com/other/Eltro-1967/index.html http://www.wendycarlos.com/other/Eltro-1967/index.html Boutique DSP developer Sean Costello has done a great series of articles here: https://valhalladsp.wordpress.com/2010/05/06/digital-pitch-shifting-early-work/ https://valhalladsp.wordpress.com/2010/05/06/digital-pitch-s...