Music harmony can be described in several ways. For a basic definition, harmony is simply two or more pitches played simultaneously. This is how basic chords are built. By combining multiple pitches, usually at least three, a chord is formed. There are a thousand different types of chord, even though many of these don't appear in Western music.

Harmony is also defined as the counterpart to melody. For example, by adding a melodic line a major or minor third above the melody, a harmony is created. Whether the third is major or minor depends entirely on the scale used in the melody and chord progression. Using the wrong kind of third results in a musical clash, or dissonance.

Different kinds of harmonic structure result from using different intervals. The fifth is a commonly used harmonic device. This results from adding a note a fifth above the melody and is very universal. Most scales tones can be separated by a fifth, so there aren't as many odd notes using this type of harmonic theory.

More complex harmonic structures require a greater knowledge of musical theory. Using the seventh is common to give the melody more of a blues or jazz feel. Jazz harmonies can often be quite complex, spanning the octaves to add ninths, 11ths or 13ths. These intervals can be hard to keep in tune when performed by vocalists, as the span between notes is great. Great vocal groups often use harmony to create chords with their voices.

One argument about harmony versus dissonance lies in the perspective of the listener. An extremely dissonant group of notes may sound absolutely beautiful to one set of ears, while sounding completely terrible to another. A lot of non-Western and avant-garde music uses the concept of dissonance to great effect. For example, a melody that begins with the C note may have C# an octave above it added. To certain listeners, this sounds absolutely frightful, while others sing its praises. Harmony is in the eye of the beholder.

Different harmonic ideas can be presented by using inversions. Inversions involve taking the lowest tone of a chord and transposing it up an octave. For example, a C major chord consists of the notes C, E and G. Taking the lowest tone, the C, and moving it up an octave creates the same chord with the notes E, G and C. This gives a different harmonic feel to the chord, allowing different notes to stick out more than others. This technique is very useful when devising harmonic movements.

Musical harmony is a simple concept, yet it contains so many variations that it is inexhaustible. With these simple rules, anyone can learn the basics of harmonization and be on their way to composing the next great song.