Continuing the discussion from Chord feature suggestions:
[quote=“oscarwildone, post:5, topic:95, full:true”][…] I understand that F Lydian has the same chords as C Major but how did you work out that you borrow from Locrian?
It appears that a lot of Hookpad users have difficulty using supermodal chords where necessary. Some would resort to using secondary chords where possible (clearly they do not encompass all 12 root pitches, and they also have lost the meaning of secondary chords), but in order to create something like this, here are two methods to access these supermodal chords:
The first method: It is important to realize that borrowing a chord from another mode is effectively the same as transposing the diatonic scale, which in turn is equivalent to temporarily changing the key signature by adding or removing a number of sharps or flats. We arrange all the 7 diatonic modes in order of the number of accidentals applied, relative to the Locrian mode, although this will work using any other diatonic mode as a reference point:
Lydian Major Mixolydian Dorian Minor Phrygian Locrian 6 5 4 3 2 1 0
Also one should remember that, for diatonic key signatures, a sharp is equivalent to raising the tonic by a fifth, and a flat by a fourth. Using the key of C as an example, all 12 keys can be reached by adding the following numbers of sharps (+ve) or flats (-ve): (both F♯ and G♭ can be reached but they are enharmonic)
C Db D Eb E F [F# Gb] G Ab A Bb B 0 -5 2 -3 4 -1 [6 -6] 1 -4 3 -2 5
In borrowing a chord from another mode, the change in the key signature due to the modes simply needs to match that due to transposition. The tonic of the current key does not matter. Here are some examples:
To get A7 in the key of D Minor, which has C7, we have to transpose this dominant seventh chord by three semitones downwards. From the circle of fifths we know that A is reached from C by raising 3 fifths. Now the Minor mode has 2 sharps (relative to Locrian), and we want a mode containing 2 + 3 = 5 sharps (relative to Locrian). We find V7 (A7) by borrowing from the Major mode.
To get D7 in the key of F Major, which has C7, we need to borrow from a mode that has 5 + 2 = 7 sharps - but that is impossible since the most sharpened mode, Lydian, has 6 sharps. Instead, we temporarily switch to a more flattened relative mode in the key menu, and from there we can access D7. For example, if we change to G Dorian, we only need a mode with 3 + 2 = 5 sharps, therefore we could find V7 (D7) by borrowing from the Major mode, which becomes IV7</sup< once we return our Theorytab to the key of F Major.
To get B7 in the key of F Minor, which has E♭7, we need to borrow from a mode that has 2 - 4 = -2 sharps (2 flats); so we switch to the relative A♭ Major, and then borrow from Phrygian that has 5 - 4 = 1 sharp, and ♭III♭7 (B7) will be there.
Tritone substitution for any chord can be achieved by transposing the current chord by 6 fifths or 6 fourths. In C Major, to get the tritone substitution of G7, we can reach ♯I7 (C♯7) by borrowing the Lydian ♯II7 from B Locrian, or reach ♭II♭7 (D♭7) by borrowing the Locrian ♭VI♭7 from F Lydian.
The second method: For more experienced users it might be even easier to remember only the transposition between modes, as in this table of semitones of the relative tonics transposed upwards from the tonic in the Major:
Major Dorian Phrygian Lydian Mixolydian Minor Locrian Major 0 2 4 5 7 9 11 12
Now the inverse transposition due to the mode will have to match the transposition of the chord’s root pitch. For instance, to get B7 in C Major, we transpose G7 upwards by 4 semitones, or downwards by 8 semitones. We notice that borrowing from the Major mode in the relative Phrygian mode does give us V7 (B7) since Major = 12, Phrygian = 4, and 12 - 4 = 8. Here is the full transposition table, using the abbreviations from the Trends API: (“I” represents Major; once again, borrowing from Lydian in Locrian is enharmonic to borrowing from Locrian to Lydian)
To I D Y L M b C From I 0 2 4 5 -5 -3 -1 D -2 0 2 3 5 -5 -3 Y -4 -2 0 1 3 5 -5 L -5 -3 -1 0 2 4 6 M 5 -5 -3 -2 0 2 4 b 3 5 -5 -4 -2 0 2 C 1 3 5 -6 -4 -2 0
Hopefully this will assist many Hookpad users in fully utilizing Hookpad’s capabilities. Last words:
- If a supermodal chord of the Major mode has the same constituent notes as a secondary chord (e,g, III7 and V7/vi in Major), it will be recognized as such in the Trends API. Other supermodal chords are currently unsupported in the Trends API.
- Borrowed chords of the Major mode that are identical to the non-borrowed chords are counted as separate entries in the Trends API, for example Lydian I7 (“L17”), Mixolydian vi (“M6”) etc.
- Similarly, two borrowed chords in the Major mode that are identical will be regarded as separate chords nonetheless, for example the Dorian, Minor, and Phrygian i (“D1”, “b1”, “Y1”).
- Switching modes “around” may raise or lower all melody notes by an octave due to a Hookpad bug.