A musical scale consists of seven notes and the octave note of the root, the first note of the scale. Musical notes run from A to G, then back to A, with half-step intervals between denoted by "#" for sharps and "b" for flats. The name for a full cycle of notes is an octave, for eight. For example, a C major scale would run C, D, E, F, G, A, B and c, the octave.
A chord consists of a group of notes played simultaneously with the same instrument to produce the effect of harmony. According to How Music Works, chords consist of at least three notes. The most common chord, a major triad, consists of the root note, the third interval and the fifth interval. The octave note sometimes remains absent, but can add a harmony to the root note.
The notes of a chord determine its scale. In the major C triad example, C, E and G act as root, third and fifth. The second plays as D, the fourth as F and the sixth and seventh as A and B. Conversely, if you know a scale, you can take its separate tones and construct a chord.
Although Western music uses the major scale most often, minor chords make an appearance when the song needs to sound darker or more melancholy. Minor chords have diminished thirds. Therefore, a C chord would drop its E to E flat, and the scale progression would read as C, D, Eb, F, G, A, B and C. If you also lower the fifth or seventh of a major scale, you create a diminished chord.
Augmented chords typically sound tense and dissonant. An augmented chord has its fifth augmented, or raised a half-step. This creates equal half-step intervals between the tones, so any note can form the basis of the chord. Scales built from augmented chords commonly feature in jazz or blues.