The dualo principle
Harmony simplifier
Arranging the notes that sound good together next to each other, the dualo principle makes it easier to visualize and play chords and scales.
A mathematical approach of harmonic objects
The dualo principle is a concept for arranging notes in the plan. This arrangement of notes can use the traditional staff as a support with the dualo key to indicate the relative pitch of notes (degrees) rather than their absolute pitch.
By default, the first degree is on the right on a line spacing, but it could perfectly well be represented on the left and / or on a line (depending on the tonic and octave chosen on the du-touch, the first degree will be located on left or right keyboard).
The degrees alternate on each side, one per row of keys on the du-touch keyboard, one per finger (from index finger to little finger) of each hand.
Degrees
Thirds
major inward
minor outward
The dualo principle puts even degrees on the same side, odd degrees on the other. Thus, the thirds are arranged vertically on the keyboard.
There are two types of thirds: major thirds and minor thirds, a semitone separates them. Thus, the semitones are arranged horizontally on the keyboard (sharps inward, flats outward).
This orientation is the same across the entire keyboard, which can be seen as a vector space generated by major and minor thirds.
More generally, here are the intervals, which also remain the same for any root note; we say that the keyboard is isomorphic.
Intervals
Therefore, chords are represented by simple, symmetrical shapes from keyboard to keyboard. Here are the main examples:
Chords: triads
(three-tone chords with two consecutive thirds / root + third + fifth)
Chords: tetrads
(four-tone chords with three consecutive thirds / root + third + fifth + seventh)
Scales
(here a major scale, with the color code of the du-touch keyboard: tonic in orange, other notes of the scale in green)
From two tetrads, it is possible to build a scale (with 7 notes). By placing a chord on each keyboard (and therefore in each hand), it suffices to play their individual notes, following the degrees, to reconstitute this scale.
In addition, the backlit keys of the du-touch allow you to highlight a scale among the most common modes (major, minor, dorian, etc.), or to draw your own scale (custom).
When we apply this principle to design a physical keyboard like the du-touch one, here is a possible arrangement of the notes (12 semitones per octave in equal temperament), assembled around the C major scale by convention.
As for the degrees, we find the same note and its alterations on the same line (ex: fb, f, f#, f##).
The du-touch is the first instrument to use the dualo layout. It has been declined in two models: the du-touch (released in 2015) and the du-touch S (released in 2017). Apart from their number of octaves, their respective keyboards are different as to the notes that compose them.
Notes: du-touch S
Each side of the keyboard is partially chromatic.
The keyboards are thus more complementary (ex: Ebb = D).
Notes: du-touch
Each side of the keyboard is fully chromatic.
It is particularly preferred among pianists, who thus have all the notes on one side as well as the other; ideal for playing complex chords and their inversions with one hand.
On a physical dualo keyboard, it is of course possible that one or more intervals must be found on the opposite keyboard (and therefore played with the other hand); this is particularly the case for chords having its root note located at the edge of one of the keyboards (as here, the F#dim7 or Gbdim7 chord). It is nevertheless possible to transpose (that is to say to shift uniformly by one or more semitones) all the notes in the parameters of the instrument, in order to find the comfort of playing an entire chord on a single keyboard.
Jules Hotrique, inventor
Mathematician and musician passionate about musical harmony, it is by retuning a sanza (African thumb piano, also known as mbira or kalimba) that he comes up with the idea of arranging harmonious notes, thirds, next to each other. Using mathematics, he ended up designing the dualo keyboard as it exists today, and immediately decided to make an instrument …
Alternative layouts
Piano (Jankó) and accordion (2 chromatic variants)
Try out the other isomorphic keyboards available in the du-touch settings.