The most basic unit of harmony is an interval. An interval is the measured distance between any two notes. If two notes of the interval are played simultaneously, they form a harmonic interval. If they are played consecutively, they form what is known as a melodic interval. Melodic intervals can sometimes imply harmony, even though they are not officially harmonic. For example, if you break up a “chord” (another name for a distinct harmony) by playing each note separately but consecutively, you are playing what's known as an arpeggio or broken chord. Arpeggios have clear harmonic underpinnings.

Because of the specific acoustical relationships between particular notes, certain intervals create more consonant (pleasant) resonances than others. In general, the more consonant intervals form the basis of complex harmonies known as chords. The primary expression of harmony is generally regarded as the triad. Triads are three-note chords (or arpeggios) utilizing the consonant intervals of thirds and fifths. The alphabetical name and origin of a triad is known as its root and serves a similar function as the tonic of a scale or key except that the root grounds each chord regardless of the overall key. Half-step alterations to specific notes in the triad, excluding the root, result in variant chord types. In other words, through varying the intervals, you can take any set of three notes and make them major, minor, augmented, or diminished.

What is a major or minor chord?

Major and minor triads are probably the most well-known chords. A major triad is composed of a root, a major third, and a perfect fifth. The major third gets its name because it is a major third interval above the root (or four half steps). The perfect fifth is a perfect fifth interval above the root (or seven half steps). To make the triad minor, simply drop the third interval by one half step. For example, C to E is a major third. To find the minor third, lower the E to an E-flat.

Major and minor chords are an important part of most music. They often evoke general emotions such as sadness, happiness, fear, or contentment. A major triad can often encourage positive emotions while minor triads are known to spark more negative connotations. As you more consciously recognize and compare the sounds of major and minor triads in use, you'll get a better sense of these possibilities. Try playing the triads in Figure 5-1 to get a sense of what these chords sound like on the bass and how they can be played.

Figure 5-1.

Major and minor triads in G