Composition and Arrangement
This domain tests melody writing, chord choice, cadences, rhythm, instrumentation and arranging for practical forces. A good answer has a clear key, singable phrases and a purposeful ending, not a string of random notes.
Melody writing
Use 4- or 8-bar phrases, stepwise motion and a clear climax. The antecedent phrase often ends on V or an imperfect cadence; the consequent ends on I or a perfect cadence. Repeat a rhythmic motif so the melody sounds unified.
Harmony and bass
Put chord tones on strong beats and passing or neighbour notes on weak beats. In C major: I is C-E-G, IV is F-A-C, V is G-B-D. Avoid doubling the leading note. For classroom arrangement, keep ranges practical and check transposition: a B flat instrument sounds a major 2nd lower than written.
Worked example
A 4-bar melody in C major has F and A in bar 3 and ends on C in bar 4. Choose IV then I. Reason: F and A are chord tones of IV, and C is the tonic. If bar 3 has D on a strong beat, V may fit better because D belongs to G-B-D. Do not force every melody note into a chord; a weak-beat D can be a passing note.
Traps
Do not end on an unstable chord. Do not write parallel fifths or octaves between outer parts in a stylistic exercise. Check instrument ranges and transposition. A cadence must match the phrase ending, not just the final bar.