To create rich, layered sounds in music, you often combine several notes played at the same time. This is the foundation of chords and harmony. A chord is a group of notes, typically three or more, played together to produce a harmonious sound. For example, a C major chord consists of the notes C, E, and G. When these notes are played simultaneously, you hear the full, pleasing sound of the chord rather than just individual notes.

In digital music production, playing several notes at once is called polyphony. In Tone.js, the PolySynth instrument makes polyphony easy. While a regular synthesizer (Synth) can only play one note at a time, PolySynth manages multiple synthesizer voices so you can trigger several notes together. This means you can play full chords, complex harmonies, or even layer melodies and bass notes for a richer musical texture.

When you use PolySynth, you specify the notes you want to play as an array, and Tone.js handles triggering each note on its own synthesizer voice. This allows you to experiment with different chord shapes, progressions, and harmonic ideas, opening up a world of musical possibilities in your browser.