Locrian vs. Phrygian

Both of these start on C, and both hold the flat second that makes a scale sound unsettled right from its first step off the tonic.

The wheel makes the difference positional rather than verbal: the fifth-degree wedge sits one wedge further clockwise in Phrygian, and the spoke drawn from the center recolors to the interval that degree now forms with the tonic. Everything else on the two wheels is identical.

That single degree is the difference between a scale that can support a stable tonic chord and one that can't: Locrian's flat fifth makes its own tonic triad diminished, the only common mode where that's true, while Phrygian's perfect fifth gives it an ordinary minor tonic underneath the same unsettled second. Reading it is one thing; the difference is much more obvious held under a drone, which is what the links under each figure are for.