Modulation can be more or less difficult, depending on how far apart the two keys are in the circle
of fifths:
• The only difference between C major and G major is that in G major the note F is sharp
(F#); therefore, C major and G major share a lot of chords, and switching from one to the
other should not be too difficult
• Similarly, the only difference between C major and F major is that in F major the note B is
flat (Bb). These two keys are again very close to each other
• The only difference between G major and D major is that in D major the note C is sharp
(C#); this makes G major and D major neighbors, but modulating from C major into D
major will be slightly more complicated because the two keys are wider apart.