How does Bach keep the theme sounding fresh throughout the movement?

Bach maintains the freshness of the theme throughout a movement by presenting it in different keys. This technique, often referred to as modulation, allows the composer to explore various harmonic landscapes while still retaining the essence of the original theme. Each key offers a unique color and emotional context, which keeps the listener engaged and allows the theme to be perceived in new and interesting ways.

By shifting the theme into different keys, Bach not only showcases his compositional skills but also enhances the thematic material's development. This approach is characteristic of his work, where he frequently manipulates themes to breathe new life into them and develop musical conversations throughout the composition. Exploring themes through modulation enables a dynamic interplay of tension and release, further enriching the listener's experience.