A scale that is Relative shares the same notes but not the same tonal center or key.  For example the scales of C Major and D Dorian are relative as:

  • C Major –   C . D . E . F . G . A . B . C
  • D Dorian – D . E . F . G . A . B . C . D

Because of the tonal center shift the distances between the notes in the two scales become different as:

  • C Major –   Tone, Tone, Semitone, Tone, Tone, Tone, Semitone
  • D Dorian – Tone, Semitone, Tone, Tone, Tone, Semitone, Tone

It is in fact these relationships that give a scale its character so even though scales may share the same notes it is the emphasis of Key or Tonal Center that provide the scales identity.  There would in fact be 6 scales that are relative to C Major, each with its own harmonic and melodic characteristics:

Scales relative to C Major – D Dorian, E Phrygian, F Lydian, G Mixolydian, A Aeolian (Natural Minor), B Locrian