AudioParam: linearRampToValueAtTime() method

linearRampToValueAtTime(value, endTime)

// create audio context
const audioCtx = new AudioContext();

// set basic variables for example
const myAudio = document.querySelector("audio");

const linearRampPlus = document.querySelector(".linear-ramp-plus");
const linearRampMinus = document.querySelector(".linear-ramp-minus");

// Create a MediaElementAudioSourceNode
// Feed the HTMLMediaElement into it
const source = audioCtx.createMediaElementSource(myAudio);

// Create a gain node and set its gain value to 0.5
const gainNode = audioCtx.createGain();

// connect the AudioBufferSourceNode to the gainNode
// and the gainNode to the destination
gainNode.gain.setValueAtTime(0, audioCtx.currentTime);
source.connect(gainNode);
gainNode.connect(audioCtx.destination);

// set buttons to do something onclick
linearRampPlus.onclick = () => {
  gainNode.gain.linearRampToValueAtTime(1.0, audioCtx.currentTime + 2);
};

linearRampMinus.onclick = () => {
  gainNode.gain.linearRampToValueAtTime(0, audioCtx.currentTime + 2);
};