BOSS XS-100 Poly Shifter | Sound Examples - YouTube Watch OnWhat were the roots of the XS series? (Image credit: Photo courtesy of Matt Knight)What would you say is at the heart of the XS series pedals? So the XS pedals feel like an extension of your playing, rather than an effect on top of what you’re doing. With XS-100, we said, ‘Yes, we need all of those minor tweaks to really dial in the sound. (Image credit: Future/Phil Barker)Let’s say there’s someone reading this who last used a pitch shifter back in the 90s.