Have you ever listened to a choir perform? Most of the time, we're used to listening to one singer sing a song. But a choir is filled with dozens — sometimes hundreds — of voices that all blend together to make a beautiful sound.
If the voices all sound wonderful together, we marvel at their harmony. The word “harmony" is often used generally to refer to things that fit or go well together. For example, peas and carrots in a stew fit together in perfect harmony.
Musically, harmony refers specifically to anything that accompanies the melody. The melody is the series of notes that makes up the main part of the music. You can think of the melody as the tune, or the recognizable main part of a song.
Harmony consists of the notes or chords played along with the melody. Harmony adds feeling to the melody. For example, you can play a melody with different harmonies and it will sound different and elicit different feelings in the listener.
One of the most basic harmonies in music is called the major triad. The major triad is formed by playing the first, third and fifth notes of the major scale simultaneously. It has what most people describe as a “happy" sound.
The same melody can be played with the major triad and sound happy, while it would sound sad when played with the minor triad. In both cases, the melody is the same, but the harmony created by the accompanying chords changes the feeling of the music.
When things sound pleasing to our ears, we say that they are consonant. Not all harmonies are consonant, though. Sometimes composers purposefully add in harmonies with other qualities to add tension to their music. We call these sounds that aren't so pleasing “dissonant."