To illustrate: we have the lettered notes, A B C D E F and G. Most of these are an entire step apart (2 frets.)
Between A and B, there is A# or Bb
Between C and D, C# or Db
D and E have D# or Eb
F and G have F# or Gb.
However, there are no notes between E-F and B-C, meaning these pairs are only 1 fret apart.
So, this means that E# is actually just a basic F, and Fb is just a basic E.
Our lives are one, colliding up and beyond
In this fatal possibility
~Coheed and Cambria, Gravity's Union
In this fatal possibility
~Coheed and Cambria, Gravity's Union