Note in an octave

[Michael Jorgensen]

 You're all not quite right,
       The octave does not divide into six whole tones, but five whole
tones plus a diminished third!  Example: C D E F# G# A# C.   A#-C is a
diminished third because a whole tone must be written B flat to C.
Granted A#-C is an enharmonic spelling of the same physical interval on
the keyboard, but would be marked an error on a theory exam.  A# and B
flat are "enharmonic tones" because they refer to the same keys on the
keyboard.  Note that enharmonic tones have nothing to do with
inharmonicity.   Music has both sharps and flats because of temperament
and tuning.  Equal temperament is the only temperament where the whole
tone is a uniform interval.

-Mike Jorgensen RPT and survivor of music theory.