KindEditor.lang({
 audio : 'MP3'
});
 KindEditor.options.htmlTags['audio'] = ['src','controls','autoplay','type'];
 KindEditor.options.htmlTags['source'] = ['src','controls','autoplay','type'];

KindEditor.ready(function(K) {
editor = K.create('#info,#spread_info', {
  //其他配置省略...
  items : [
    'source', '|', 'undo', 'redo', '|', 'preview', 'print', 'template', 'code', 'cut', 'copy', 'paste',
    'plainpaste', 'wordpaste', '|', 'justifyleft', 'justifycenter', 'justifyright',
    'justifyfull', 'insertorderedlist', 'insertunorderedlist', 'indent', 'outdent', 'subscript',
    'superscript', 'clearhtml', 'quickformat', 'selectall', '|', 'fullscreen', '/',
    'formatblock', 'fontname', 'fontsize', '|', 'forecolor', 'hilitecolor', 'bold',
    'italic', 'underline', 'strikethrough', 'lineheight', 'removeformat', '|', 'image', 'multiimage',
     '|' ,'table', 'hr', 'emoticons', 'baidumap', 'pagebreak',
    'anchor', 'link', 'unlink', '|', 'about','audio'
  ]
});

<style>
  .ke-icon-audio {
    background-position: 0px -528px;
    width: 16px;
    height: 16px;
  }
</style>

kindeditor/plugins/audio/audio.js

plugins/media/media.js

/**
 * Created by admin on 15-5-6.
 */

KindEditor.plugin('audio', function(K) {
  var self = this, name = 'audio', lang = self.lang(name + '.'),
    allowMediaUpload = K.undef(self.allowMediaUpload, true),
    allowFileManager = K.undef(self.allowFileManager, false),
    formatUploadUrl = K.undef(self.formatUploadUrl, true),
    uploadJson = K.undef(self.uploadJson, self.basePath + 'php/upload_json.php');
  self.plugin.media = {
    edit : function() {
      var html = [
        '<div style="padding:20px;">',
        //url
        '<div class="ke-dialog-row">',
        '<label for="keUrl" style="width:60px;">MP3 URL</label>',
        '<input class="ke-input-text" type="text" id="keUrl" name="url" value="" style="width:160px;" /> &nbsp;',
        '<input type="button" class="ke-upload-button" value="上传" /> &nbsp;',
        '</div>',

        '</div>'
      ].join('');
      var dialog = self.createDialog({
          name : name,
          width : 450,
          height : 230,
          title : self.lang(name),
          body : html,
          yesBtn : {
            name : self.lang('yes'),
            click : function(e) {
              var url = K.trim(urlBox.val()),
                width = widthBox.val(),
                height = heightBox.val();
              if (url == 'http://' || K.invalidUrl(url)) {
                alert(self.lang('invalidUrl'));
                urlBox[0].focus();
                return;
              }
              if (!/^\d*$/.test(width)) {
                alert(self.lang('invalidWidth'));
                widthBox[0].focus();
                return;
              }
              if (!/^\d*$/.test(height)) {
                alert(self.lang('invalidHeight'));
                heightBox[0].focus();
                return;
              }
              var html = '<p><audio src="/UploadFiles/2021-04-02/'+url+'">

至此，整个插件基本结束。
需要注意的是，上传文件用的是通用的配置uploadJson参数，但会在上传的时候自动添加一个get参数 "dir=audio" ，以便后台识别：


url : K.addParam(uploadJson, 'dir=audio'),