  //
    // Convert TeX to MathML with speech labels
    //
    async convert() {
      //
      // Disable controls while we are processing.
      //
      Interactive.enableControls(false);
      //
      // Get the TeX expression and the output area.
      //
      const input = document.querySelector('#input').value.trim();
      output = document.querySelector('#mml').firstChild;
      //
      // Get the MathML with speech.
      //
      const mml = await MathJax.toSpeechMML(input, {
        display: