What are chord progressions and cadences?
A chord progression is a series of chords played in a sequence. When identifying chords within a progression, the main task is to find their harmonic functions within the key, which means to compare the chord to the tonic of the key. The harmonic functions are written with the Roman numerals I, II, III, IV, etc. Each numeral stands for its corresponding degree within a scale. Therefore, identifying the degree of a chord progression involves your abilities to identify intervals accurately.
All of the seven degrees of the major and minor scales can serve as the root of a triad. The triads on the “tonal” degrees of the scale (I, IV and V) are the most important for establishing the tonality of a piece.
Below is shown the seven degrees of a C major scale:
I (C major), II (d minor), III (e minor), IV (F major), V (G major), VI (a minor), VII (b dim)