Chromatic Refers to note going up or down a semitone.
Dorian the tonic is D. The semitones are between the second and third and the sixth and seventh degrees.
Ionian the tonic is one. The semitones are between the third and fourth and the seventh and eighth degrees.
Lydian the tonic is four. The semitones are between the fourth and fifth and the seventh and eighth degrees.
Mixolydian the tonic is five. The semitones are between the third and fourth and the sixth and seventh degrees.
Phrygian the tonic is E. The semitones are between the first and second and fifth and sixth degrees.
Tetrachord The difference in sound between a tone and a semitone is vitally important in music. A good way to practise hearing the difference is to begin on the A above middle C and then sing or play a whole tone down to G, another whole tone down to F and a semitone down to E. This pattern is called a tetrachord. The same pattern of two descending tones followed by a semitone can be begun on E, going down to B.
