Quick questions on Pitch, scales, intervals and chords: HSC Music core

A scale is an ordered set of pitches. The major scale follows the tone pattern T T S T T T S (for example C major: C D E F G A B C). The natural minor uses T S T T S T T (A minor: A B C D E F G A). The harmonic minor raises the seventh, giving a distinctive augmented-second gap (A B C D E F G-sharp A), and the melodic minor raises the sixth and seventh ascending but reverts descending.

An interval is the distance between two pitches. Name it by number (count the letter names inclusively) and quality (major, minor, perfect, augmented, diminished). The perfect intervals are the unison, fourth, fifth and octave. Seconds, thirds, sixths and sevenths come as major or minor.

A triad is a three-note chord built in thirds: root, third and fifth. The four triad qualities are major (major third plus minor third, for example C E G), minor (minor third plus major third, C E-flat G), diminished (two minor thirds, C E-flat G-flat) and augmented (two major thirds, C E G-sharp). In a major key the triads on each degree are: I major, ii minor, iii minor, IV major, V major, vi minor, vii diminished. Knowing this lets you predict which chords belong to a key.

Adding a fourth note a third above the fifth gives a seventh chord. The dominant seventh (V7, for example G B D F in C major) is the engine of tonal harmony because it pulls strongly back to the tonic. The major seventh (C E G B) sounds lush and is common in jazz and ballads; the minor seventh (C E-flat G B-flat) is common in funk, soul and jazz.