Playing in harmony with others requires everyone to have a fairly decent knowledge of music plus the technical skill and timing perfection. Until harmony pedals were a thing, pitch shifters were our best hope as we'd simply set them to a third above and stick to the pentatonic scale ... No fancy shredding here please.
Now though the cleverest companies have developed amazing algorithms allowing us to choose not only the intervals but even the key, which with a little modal knowledge can open up all sorts of exotic harmonic goodness.
But why would you stop there? Well BOSS didn't, they proceeded to include a detune mode which is essentially chorus and the S-Bend for those of us not happy with machines. The trick with this pedal has always been the blend, too much and it'll sound far too obvious but blend it in just under your direct tone and enter musical bliss.