Melodic and Harmonic Intervals
An interval is the measured distance between any two notes. If two notes are played in succession, they form what is known as a melodic or linear interval. If these notes are played simultaneously, they form a harmonic or vertical interval. Melodic intervals can sometimes imply harmony, as you will learn later in the book. Figure 5-6 shows an example of melodic and harmonic intervals.
FIGURE 5-6: Melodic and harmonic intervals
Figure 5-7 shows essential intervals. You will use these continually when you compose music. In this figure, you will see a perfect unison, a major second, a major third, a perfect fourth, a perfect fifth, a major sixth, a major seventh, and a perfect octave shown as melodic intervals. Other essential intervals include: minor second, minor third, minor sixth, minor seventh, augmented fourth, and diminished fifth; the last two intervals are also called tri-tones. These are shown in Figure 5-8.
FIGURE5-7: Essential intervals
FIGURE5-8: Other essential intervals
There are still other intervallic relationships made possible through the beauty of enharmonics. Some of these include augmented unisons, augmented thirds, and diminished octaves. While these may be found in notation, the naming of intervals using these terms is more or less academic. In Chapter 6, you will encounter additional intervals in the form of harmonic extensions.
To understand what intervals really mean, count them using the smallest unit of measurement, which in western music are half steps or semi-tones. When you count intervals in this way you are moving chromatically. On a piano, chromatic movement means that you play every white and black key as you move up or down the keyboard. On a guitar, this means depressing every successive fret on any given string.
When determining intervals using half steps, you will see that a minor second contains two half steps, a major second contains three half steps, a minor third contains four half steps, a major third contains five half steps, a perfect fourth contains six half steps, and so on. In order to accurately count steps you must begin counting on the first note. For example, if you're moving up chromatically from C to A, you would count: C (1), C# (2), D (3), D# (4), E (5), F (6), F# (7), G (8), G# (9), A (10). There are a total of 10 half steps between C and A.
In equal temperament tuning—as defined later in the chapter—an enharmonic is any pair of notes that sound the same but are called two different names. For example, an F# may also be called a G and a B# may be called a C natural. Enharmonic naming depends on musical context. Enharmonics may also be applied to key signatures.
You should also know how to count whole steps. Like half steps, when counting whole steps, you must begin on the first note. When you count whole steps, you will count every other note in the chromatic scale. For example, C to D is a whole step (skipping C#). E to F# is another example (skipping F natural). Whole steps can also be called major seconds.