Tetra Chords 

 

                        Tetra chords can be used to access many 7 note scales.  A tetra chord is a pattern of 4 notes spaced out over 5 half steps.  When we combine two tetra chords, we create a seven note scale.  Each tetra chord contains 3 intervals that add up to 5.  The numbers refer to the number of ½ steps apart each note is.  For example, we will use a 2-2-1 tetra chord pattern.  The three interval numbers add up to 5 (2 + 2 + 1).    So, if we start from C, and apply the tetra chord, we get the following:

 

C                     D                     E                      F

            2                      2                      1

 

            From our 221 tetra chord in C, we get the notes C, D, E, and F.  The distance from C to F is five half steps, and we have used four notes in that span, and three different intervals.  To make this a full 7 note scale, we need to add another tetra chord to it.  We do this by using a whole step to connect the two tetra chords, and then repeat the same process.

 

F                      G                     A                     B                      C

  Whole step               2                      2                      1

   Connector

 

 

            When we put the two patterns together, we get the notes C, D, E, F, G, A, B, and C, otherwise known as the C major scale.  So, the pattern of half steps and whole steps used to create a major scale is 221 2 221.  We have a tetra chord (221) a whole step connector (2) and another tetra chord (221).  To create different scales, we can use different tetra chord patterns.  The following is a list of all of the possible tetra chords:

 

221      Major

212      Minor

122      Negative

131      Harmonic

113      Harmonic Negative

311      Harmonic Positive

 

            We can mix and match any two tetra chords to form a seven note scale.   For instance, let’s use 122 (Negative), and 311 (Harmonic Positive).  That would create the following scale in C:

 

C                     Db                   Eb                    F                      G                     A#                   B                      C

            1                      2                      2              Whole Step              3                      1                      1

                                                                            Connector

 

            So, we get C, Db, Eb, F, G, A#, B, C…quite unusual.  In tetra chord theory, this scale would be called C Negative Harmonic Positive.  We use the key note (C in this case), followed by the name of the first tetra chord (Negative), followed by the name of the second tetra chord (Harmonic Positive).  Using this naming method, the major scale we created above would actually be called C Major Major.  It seems a bit unnecessary at first since we all are familiar with the major scale, but when we start building more unusual scales it helps greatly to be able to recognize the scale by the quality of each tetra chord.

            Here are some scales that I like to utilize.  Some of these have equivalents in more traditional theory, and some are pretty unique.  I will give the name, the formula, build the scale from C and give an equivalent name, if it exists:

 

 

Name

Formula

Scale notes from C

Equivalent to:

Harmonic Negative

131 2 122

C Db E F G Ab Bb C

Mixolydian mode of Harmonic Minor or Jewish Minor

Minor Major

212 2 221

C D Eb F G A B C

Melodic Minor

Harmonic Harmonic

131 2 131

C Db E F G Ab B C

 

Major Negative

221 2 122

C D E F G Ab Bb C

Mixolydian mode of Melodic Minor

Minor Harmonic

212 2 131

C D Eb F G Ab B C

Harmonic Minor

Harmonic Negative Minor

113 2 212

C Db Ebb F G A Bb C

 

Major Minor

221 2 212

C D E F G A Bb C

Mixolydian Mode

Negative Negative

122 2 122

C Db Eb F G Ab Bb C

Phrygian Mode

Minor Minor

212 2 212

C D Eb F G A Bb C

Dorian Mode

Major Major

221 2 221

C D E F G A B C

Major scale (Ionian Mode)

Minor Negative

212 2 122

C D Eb F G Ab Bb C

Natural Minor (Aeolian Mode)

Harmonic Positive Harmonic Negative

311 2 113

C D# E F G Ab Bbb C

 

 

 

            There are many more scales you can come up with on your own.  Also, you can find a whole new set of variants by playing the modes of these scales.  For instance, try playing the C Harmonic Harmonic scale, except starting on the note Db (Db E F G Ab B C Db).  You’ve just played the Dorian mode of the Harmonic Harmonic scale.  This kind of variant opens up a whole new set of patterns.