Make the theory
make sense.

The numeral gives scale degree; uppercase means major, lowercase means minor, and ° means diminished. In G major: I = G–B–D, ii = A–C–E, vii° = F♯–A–C.

Triads: root position = 5/3 (usually omitted), first inversion = 6, second inversion = 6/4.

Sevenths: root position = 7, first inversion = 6/5, second inversion = 4/3, third inversion = 4/2. Identify the bass before placing upper voices.

Read V7/ii as “five-seven of two.” Find the target chord, treat its root as a temporary tonic, then build its dominant seventh. In G major, ii is A minor, so V7/ii is E–G♯–B–D.

Tonicization briefly emphasizes another chord; a modulation establishes a new key more firmly.

Major: W–W–H–W–W–W–H. Natural minor: W–H–W–W–H–W–W. Harmonic minor raises scale degree 7. Ascending melodic minor raises 6 and 7; the traditional descending form is natural minor.

Count letter names for interval number, then semitones for quality. C–F♯ is an augmented fourth; C–G♭ is a diminished fifth. Same piano keys, different spellings and functions.

Start with the required bass. Resolve a leading tone upward and a chordal seventh downward in conventional dominant-to-tonic writing. Favor stepwise motion and retain common tones when appropriate.

Avoid parallel fifths and octaves between voices, voice crossing, and excessive leaps. Keep adjacent upper voices within an octave. A list of chord tones alone does not establish good SATB voice leading.

Authentic: V–I (or V–i). Half: a phrase ends on V. Deceptive: V moves somewhere other than the expected tonic, commonly vi in major or VI in minor. Plagal: IV–I (or iv–i).

A perfect authentic cadence requires root-position V–I with the tonic in the final soprano. Chord symbols alone cannot prove that a cadence is perfect authentic.