How do sound waves work?

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• Timbre and envelope are two characteristics of sound waves that help determine why, say, two instruments can play the same chords but sound nothing alike.

• Timbre is determined by the unique harmonics formed by the combination of notes in a chord. The A in an A chord is only its fundamental note—you also have overtones and undertones. The way these sound together helps keep a piano from sounding like a guitar

• envelopes, which determine how a sound’s amplitude changes over time

• Envelopes comprise four parts: Attack, Decay, Sustain, and Release

• Attack: This is how quickly the sound achieves its maximum volume. A barking dog has a very short attack; a rising orchestra has a slower one.

• Decay: This describes how fast the sound settles into its sustained volume. When a guitar player plucks a string, the note starts off loudly but quickly settles into something quieter before fading out completely. The time it takes to hit that sustained volume is decay

• Sustain: Sustain isn’t a measure of time; it’s a measure of amplitude, or volume. It’s how loud the plucked guitar note is after the initial attack but before it fades out

• Release: This is the time it takes for the note to drift off to silence.