C Locrian scale on the guitar fretboard
The C Locrian scale is made of C (the root), Db (minor second), Eb (minor third), F (perfect fourth), Gb (diminished fifth), Ab (minor sixth) and Bb (minor seventh). The fretboard shows every one of them across the neck in standard tuning (E A D G B E), and plays them back so you can hear the scale.
The Locrian mode is the seventh mode of the major scale, with a lowered second and a lowered fifth. The lowered fifth takes away the stable fifth above the root, so it sounds unsettled. It shares its notes with a major scale a semitone above.