Represents one tone in a scale.

Attributes

• tone - A tone index from 0-11 representing the relative position of the

   tone within the chromatic scale.
  

• letter_index - A 0-6 value representing the relative letter position, which

   helps to disambiguate theoretic values such as Eb and D#.  See +Key+.
  

Key Context

key is delgated to chord to access the scale‘s key context.