Combining synthesis, effects, and user interaction allows you to create a truly interactive web-based synthesizer. In this example, you use Tone.js to generate sound with a polyphonic synthesizer, then shape the sound with real-time effects like reverb, delay, and filtering. The virtual keyboard provides a straightforward way for users to play notes, while the effect controls let users sculpt the sound as they play. This integration of synthesis, effects, and user input transforms the browser into a dynamic, playable instrument, letting anyone experiment with sound in creative and engaging ways.