Guitar
Contents
Intervals
An interval is the distance between two different pitch levels. Its type is defined by the number of notes covering the interval and its quality is defined by its size in number of tones or semitones. For a guitarist, it is necessary to visualize how these intervals are materialized on the neck, i.e. how the 2 notes of the interval are positioned in relation to each other.
The neck of the guitar is a kind of table, delimited horizontally by the 6 strings, and vertically by the frets forming the fretboard. The positioning of the notes is therefore defined in terms of string numbers and fret numbers. The melodic distance between the frets being homogeneous all along the neck (semitone), the diagram of an interval will remain unchanged whatever its horizontal translation. The melodic interval between the strings, however, is irregular: M3 between the 2nd and 3rd strings and P4 for the others. When transposing on these 2nd and 3rd strings, the diagram will be altered.
These interval diagrams are a precious help for the memorization of scale diagrams (sequence of melodic intervals) and chord diagrams (set of harmonic intervals). The fundamental interval being the octave, it is important to assimilate its different diagrams at first, to be able to position the other intervals more easily.
It is wise to memorize the intervals according to their type (3rd, 5th, etc.), their different qualities forming very close diagrams: the three possible 5th for example (b5, 5 and #5) follow each other at a distance of one fret on the same string. Ditto for the other intervals.
Melodic scales
A scale is a defined sequence of intervals, and its diagram will form a set of degrees covering a vertical portion of the neck. There are many different diagrams for the same scale, all with pros and cons. The purpose here is to provide diagrams with the least extension and the most similarity between the 3 main scales (major, melodic minor and harmonic minor) to facilitate memorization. The 5 diagrams of each scale cover an octave, thus 12 frets of the neck.
The pentatonic scale is obtained by removing 2 degrees from the heptatonic scales, forming semitone intervals. Thus, each heptatonic diagram contains its corresponding pentatonic diagram. A pentatonic scale can be constructed from the major and melodic minor scales. The harmonic minor scale (with 3 semitones) does not allow to obtain a pentatonic scale without semitones (only 2 degrees can be removed).
From the major scale, one obtains the major pentatonic (abbreviated pM and numbered: 1 2 3 5 6 ), from the melodic minor scale one obtains the melodic minor pentatonic (abbreviated pmm and numbered: 1 b3 4 5 6). The VI degree mode (see the concept of mode on the Harmony page) of the major pentatonic (numbered: 1 b3 4 5 b7) differs only by one degree from the melodic minor pentatonic. These 2 modes (VIpM and Ipmm) constitute a neighbouring stock of degrees, which can be substituted for each other in the practice of melody (improvised or not) to provide varied "colors".
In the same way, we can bring together modes IIpM and IVpmm as well as modes IIIpM and Vpmm). With the addition of the corresponding heptatonic mode, one has a possible choice of notes for practice on the main chord types (triads or tetrads).
Modes-chords
A mode is a scale polarized on one of its degrees, having then the function of tonic, pole of attraction of the other degrees. When we play this mode, we go through the degrees in a sequence of seconds, starting from this tonic.
The chord of the mode is simply obtained, also starting from this tonic (then called root of the chord) by traversing the degrees of thirds in thirds, that is to say a degree on two.
Mode and chord mode are made of the same notes, and one can improvise with these notes on this chord which plays the role of pole of attraction. By building another chord starting from another degree, this one becomes in its turn a pole of attraction, and produces another mode of the scale. In this way, one can produce as many different modes as there are degrees.
The diagrams of the scales represent fixed stocks of notes, but which can be numbered in different ways according to the degree playing the function of tonic. Each mode has its own numbering, and the chord diagram is included in the diagram of its mode.
In short, learning a scale diagram means learning this scale in all the keys (by shifting the diagram to the appropriate fret). And it also means learning all the (7) modes of each scale! It is also to facilitate the learning of chords whose diagrams are (more or less according to the type of chord) included in those of its mode. The transposing character of the guitar justifies the diagram approach.