I have a 2011 SR5 and the three sounds are quite distinctive. When the switch is back toward the bridge, the pickup coils are wired in parallel. The sound is slightly scooped or hollow. This is the classic Stingray tone as produced by the 4 strings. Toward the neck gives you the coils in series, a powerful punchy tone that I find the most useful one. And on post 2008 models, the middle position is series wiring plus a filter, which to my ears rolls off the top end and slightly accentuates the bottom. It’s a sort of vintage series sound. There’s no single coil mode after 2008.