Welcome to my Scales l Webpage.
Western music is based on twelve semitones. This system is called a chromatic scale by opposition to the diatonic scale which consists of five full-tones and two semitones placed in a specific order according to the chosen modal tonality system. (meanly major and minor). The term diatonic comes from ancient Greek music theory and means "through full tones." Ancient Greek music tuned its scales using an interval of a perfect fourth (P4) called tetrachord. A diatonic tetrachord was one that was tuned with two whole tones on the top, and the remainder left on the bottom (roughly a semitone). (See Modes and Pentachord). These tunings in ancient Greece were contrasted with chromatic methods of tuning the tetrachord, which generally involved intervals smaller than whole tones and therefore often resulted in some consecutive semitone intervals as we find in our modern chromatic scale. (See Introduction)
Figures a, b, c show diatonic C scales with their respective five full-tone and two semitones. Fig. (d) shows a C minor harmonic scale. Please note that this scale is not commonly called diatonic due to its one and a halftone between Ab and B.
Also, note the relative similarity between a major and a melodic minor scale. (Fig. a), (fig. c) No wonder that melodic minor is chosen for vocal. Also, note that Natural minor has no leading tone. (Fig. b)
Relative Minor/Major Scale.
What is a relative minor scale? The picture below shows the notes in a C major scale that continue until they reach a twelve intervals scale. The first seven notes belong to the C major scale (blue section). The other seven notes (in red), starting from degree Vl in C major, form the A minor natural scale and thus become the relative minor of C major scale. (some sort of complementary scale to C major). Please note that C major and A natural minor have no alterations. (no sharps, no flats). On the other hands, the natural minor scale starting on the sixth degree of C major scale represents the Aeolian mode.
We have also to mention the relative Major of a minor scale. Here, C natural minor and its relative Major, (EbM7). See also where the Tritone is placed in the natural minor scale.
At this point, it is essential to understand the relationship between those full and semitones alongside the tonality. Effectively, the notes that form a scale have not the same "weight". For instance, (fig l.) shows the notes C, E, and G in the C major scale which are commonly called "rest or stable notes" and thus do not "ask" to move. Whereas, (fig ll) shows notes that may be defined as "unstable or active notes" since they are attracted by either the preceding or the following note. D is attracted by either C or E and A is by G. But the most unstable notes are of course F and B and emphasis the Tritone (T). In this C scale, the B note is called, leading tone.