Listen to your web pages

sweep-swoop.js

const audioCtx = new window.AudioContext();
const oscillator = audioCtx.createOscillator();
oscillator.connect(audioCtx.destination);
oscillator.type = "sine";

let numItems = 0

oscillator.frequency.setValueAtTime(
  1,
  audioCtx.currentTime
);

oscillator.start();

const observer = new MutationObserver(function (mutationsList) {
  numItems += mutationsList.length

  oscillator.frequency.setValueAtTime(
    Math.log(numItems + 1) * 440,
    audioCtx.currentTime
  );

  setTimeout(() => {
    numItems -= mutationsList.length
    if (numItems === 0) {
      oscillator.frequency.setValueAtTime(
          1,
          audioCtx.currentTime
        )
    } else {
        oscillator.frequency.setValueAtTime(
          Math.log(numItems + 1) * 440,
          audioCtx.currentTime
        )
    }
  }, 100)
});

observer.observe(document, {
  attributes: true,
  childList: true,
  subtree: true,
  characterData: true
});

This is a slightly different version where the pitch of a single oscillator changes continuously so it's a bit more continuous.

Hahaha, even cooler. Sounds more futuristic. I'll add this as a feature to my Chrome extension.