Fugue Structure

Physics: Fugue: subject (main theme), answer (P5 transposition), countersubject (against answer), exposition (all voices enter), episode (fragmentation/sequence), stretto (overlapping entries). Real answer = exact transposition by P5; tonal answer = modified to avoid leaving key. Bach's Well-Tempered Clavier (1722/1742): 24 preludes + fugues in all 24 major/minor keys. BWV 847 (C minor): subject 2 bars, answer enters bar 3. Augmentation stretches, diminution compresses the subject rhythmically. Stretto: entries overlap by increasing degree, building tension.