How did Mozart advance the art of symphonic orchestration?

Wolfgang Amadeus Mozart significantly advanced the art of symphonic orchestration by moving toward a more integrated and expressive use of the orchestra, characterized by freer instrumentation and a departure from the rigid doubling of parts common in earlier periods.1

Key aspects of his contribution include:

• Expanded Instrumentation: Mozart introduced clarinets into his symphonic palette, notably in the Symphony in D Major (K 297, Paris), and his final two symphonies (K 550 and K 551) are considered among the most beautifully orchestrated works of the Classical era.12
• Integration of Texture: While earlier Classical practice often relied on winds to simply double string parts, Mozart’s mature works achieved a more unified and expressive texture. He utilized fuller imitation and more singing figuration, reflecting his deep experience as an opera and chamber music composer.13
• Dynamic Sensitivity: Mozart rejected the stylized "Mannheim gesture" in favor of better-integrated, nuanced dynamics.1
• Thematic Development: Unlike formal experimenters, Mozart excelled in the transformation of thematic material, using orchestration to support development sections that expanded over wider tonal fields.1