A groove spiral at a fixed pitch is a diffraction grating, which is why a plain black disc is one of the most colourful things in a room under a spotlight. The dispersion runs outward from the spindle, because the grooves run around it and a grating throws its spectrum across its lines rather than along them. Vinyl is cut far coarser than a compact disc is pressed, so the fan is gentler and wider — the same physics at a different pitch, which is most of what pitch means here.