Composers choose the notes or chords that accompany a melody carefully. This is called the harmony. Sometimes all the notes of a chord are played together; in other places they might be played one note at a time, as in arpeggios. Some harmony chords sound nice, and others can sound a bit ugly.
The stormy-sounding chords are called dissonant chords; they feel tense. They are important in music because they make you want to hear them change to a nice-sounding chord. They lead the music to somewhere else. The nice-sounding chords are called consonant. You usually want to have both in music to make it more interesting.
Harmony provides the emotions in music. It can make the music sound happy, sad, calm, angry, and any other emotion you can think of. Look at your piano music and see if you can name an emotion for each piece. Is it happy, sad, impatient?
You can make a chord from every note in a scale by adding thirds to it. To name these chords, musicians use Roman numerals, such as I ii iii IV V. When the chord is major, the Roman numerals are capital letters, and when the chord is minor, the numerals are small letters. The chords also have English names like tonic, dominant, and mediant.
Composers often use specific combinations of these chords in the harmony for their music. When they use the chords in one of these patterns, we call it a chord progression. Probably the most famous chord progression is the Amen that concludes a hymn. It uses the chord from the 4th note in the scale and the first chord (or tonic).
IV Chord = FAC (A - men)
I Chord = CEGC (A-men)
This example is based on the C major scale but the chords can be based on other scales as well. Another important chord progression that is heard in almost all rock and roll music is the I-IV-V-I. Hundreds of songs use only these three chords. (CEG / FAC / GBD)
On my other blog, I have a post on chord extensions and keyboard voicings, Chords and Harmony
You may be interested in taking a look at Hear and Play offering Gospel Keys Ministry Musician 1 featuring Jason White. He teaches gospel piano chords.
photo credit: second sax lesson via photopin (license)
Wishing you a Happy 4th!
"The beautiful thing about learning is that no one can take it away from you." B.B.King