Much textural variety with 2 parts set against 3 other parts, or 3 upper parts against 3 lower. Greater tessitura than quartets, so richer harmonic writing without heaviness or crowding. K. 515 is Mozart's longest 4-mvt. By 1789 he had arrived at a style noticeably more austere and refined, more motivic and contrapuntal, more economical in the use of material, and harmonically and texturally less rich. Possibly some influence of Haydn's late style.
Music is more complex.
Joseph de Marliave, Beethoven's Quartets . String Quartets Op. String Quintet in C Op. Fugue in D for String Quartet Op. String Quartet Op.