At 6:08 Jon describes this as a recent addition to his set up for reverb and harmonizer purposes (video date February 28, 2014). He details how he uses the harmonizer to simply pitch-shift his vocals down an octave for a "weird pseudo-artificial and yet really organic" sound for his vocals.more
After I saw someone use a harmonizer by TC Electronix live, I just had to go home and see whether BOSS had one as well, since I'm a big fan of their effect pedals. Lucky enough they did and I got it straight away. A vocalizer like that with so many different effects and possibilites is really the ultimate playground for every singer, who likes to take his vocal performance to the next level. It really changed my live performance completely and I've been using pretty much every effect for different songs, especially the Harmonizer with an additional vocal a third above my main vocal for the chorus and the Autotune, whenever I feel particularly freaky. One of the best investments I've made so far!