A CodePen by Anonymous.

script.js

/**
 *
 * SoundManager 2 Demo: Play MP3 links "in-place"
 * ----------------------------------------------
 *
 * http://schillmania.com/projects/soundmanager2/
 *
 * A simple demo making MP3s playable "inline"
 * and easily styled/customizable via CSS.
 *
 * Requires SoundManager 2 Javascript API.
 *
 */

function InlinePlayer() {
  var self = this;
  var pl = this;
  var sm = soundManager; // soundManager instance
  var isIE = (navigator.userAgent.match(/msie/i));
  this.playableClass = 'inline-playable'; // CSS class for forcing a link to be playable (eg. doesn't have .MP3 in it)
  this.excludeClass = 'inline-exclude'; // CSS class for ignoring MP3 links
  this.links = [];
  this.sounds = [];
  this.soundsByURL = [];
  this.indexByURL = [];
  this.lastSound = null;
  this.soundCount = 0;

  this.config = {
    playNext: false, // stop after one sound, or play through list until end
    autoPlay: false  // start playing the first sound right away
  }

  this.css = {
    // CSS class names appended to link during various states
    sDefault: 'sm2_link', // default state
    sLoading: 'sm2_loading',
    sPlaying: 'sm2_playing',
    sPaused: 'sm2_paused'
  }

  this.addEventHandler = (typeof window.addEventListener !== 'undefined' ? function(o, evtName, evtHandler) {
    return o.addEventListener(evtName,evtHandler,false);
  } : function(o, evtName, evtHandler) {
    o.attachEvent('on'+evtName,evtHandler);
  });

  this.removeEventHandler = (typeof window.removeEventListener !== 'undefined' ? function(o, evtName, evtHandler) {
    return o.removeEventListener(evtName,evtHandler,false);
  } : function(o, evtName, evtHandler) {
    return o.detachEvent('on'+evtName,evtHandler);
  });

  this.classContains = function(o,cStr) {
	return (typeof(o.className)!='undefined'?o.className.match(new RegExp('(\\s|^)'+cStr+'(\\s|$)')):false);
  }

  this.addClass = function(o,cStr) {
    if (!o || !cStr || self.classContains(o,cStr)) return false;
    o.className = (o.className?o.className+' ':'')+cStr;
  }

  this.removeClass = function(o,cStr) {
    if (!o || !cStr || !self.classContains(o,cStr)) return false;
    o.className = o.className.replace(new RegExp('( '+cStr+')|('+cStr+')','g'),'');
  }

  this.getSoundByURL = function(sURL) {
    return (typeof self.soundsByURL[sURL] != 'undefined'?self.soundsByURL[sURL]:null);
  }

  this.isChildOfNode = function(o,sNodeName) {
    if (!o || !o.parentNode) {
      return false;
    }
    sNodeName = sNodeName.toLowerCase();
    do {
      o = o.parentNode;
    } while (o && o.parentNode && o.nodeName.toLowerCase() != sNodeName);
    return (o.nodeName.toLowerCase() == sNodeName?o:null);
  }

  this.events = {

    // handlers for sound events as they're started/stopped/played

    play: function() {
      pl.removeClass(this._data.oLink,this._data.className);
      this._data.className = pl.css.sPlaying;
      pl.addClass(this._data.oLink,this._data.className);
    },

    stop: function() {
      pl.removeClass(this._data.oLink,this._data.className);
      this._data.className = '';
    },

    pause: function() {
      pl.removeClass(this._data.oLink,this._data.className);
      this._data.className = pl.css.sPaused;
      pl.addClass(this._data.oLink,this._data.className);
    },

    resume: function() {
      pl.removeClass(this._data.oLink,this._data.className);
      this._data.className = pl.css.sPlaying;
      pl.addClass(this._data.oLink,this._data.className);      
    },

    finish: function() {
      pl.removeClass(this._data.oLink,this._data.className);
      this._data.className = '';
      if (pl.config.playNext) {
        var nextLink = (pl.indexByURL[this._data.oLink.href]+1);
        if (nextLink<pl.links.length) {
          pl.handleClick({'target':pl.links[nextLink]});
        }
      }
    }

  }

  this.stopEvent = function(e) {
   if (typeof e != 'undefined' && typeof e.preventDefault != 'undefined') {
      e.preventDefault();
    } else if (typeof event != 'undefined' && typeof event.returnValue != 'undefined') {
      event.returnValue = false;
    }
    return false;
  }

  this.getTheDamnLink = (isIE)?function(e) {
    // I really didn't want to have to do this.
    return (e && e.target?e.target:window.event.srcElement);
  }:function(e) {
    return e.target;
  }

  this.handleClick = function(e) {
    // a sound link was clicked
    if (typeof e.button != 'undefined' && e.button>1) {
      // ignore right-click
      return true;
    }
    var o = self.getTheDamnLink(e);
    if (o.nodeName.toLowerCase() != 'a') {
      o = self.isChildOfNode(o,'a');
      if (!o) return true;
    }
    var sURL = o.getAttribute('href');
    if (!o.href || (!sm.canPlayLink(o) && !self.classContains(o,self.playableClass)) || self.classContains(o,self.excludeClass)) {
      return true; // pass-thru for non-MP3/non-links
    }
    var soundURL = (o.href);
    var thisSound = self.getSoundByURL(soundURL);
    if (thisSound) {
      // already exists
      if (thisSound == self.lastSound) {
        // and was playing (or paused)
        thisSound.togglePause();
      } else {
        // different sound
        sm._writeDebug('sound different than last sound: '+self.lastSound.id);
        if (self.lastSound) {
          self.stopSound(self.lastSound);
        }
        thisSound.togglePause(); // start playing current
      }
    } else {
      // stop last sound
      if (self.lastSound) {
        self.stopSound(self.lastSound);
      }
      // create sound
      thisSound = sm.createSound({
       id:'inlineMP3Sound'+(self.soundCount++),
       url:soundURL,
       onplay:self.events.play,
       onstop:self.events.stop,
       onpause:self.events.pause,
       onresume:self.events.resume,
       onfinish:self.events.finish
      });
      // tack on some custom data
      thisSound._data = {
        oLink: o, // DOM node for reference within SM2 object event handlers
        className: self.css.sPlaying
      };
      self.soundsByURL[soundURL] = thisSound;
      self.sounds.push(thisSound);
      thisSound.play();
    }

    self.lastSound = thisSound; // reference for next call

    if (typeof e != 'undefined' && typeof e.preventDefault != 'undefined') {
      e.preventDefault();
    } else {
      event.returnValue = false;
    }
    return false;
  }

  this.stopSound = function(oSound) {
    soundManager.stop(oSound.id);
    soundManager.unload(oSound.id);
  }

  this.init = function() {
    sm._writeDebug('inlinePlayer.init()');
    var oLinks = document.getElementsByTagName('a');
    // grab all links, look for .mp3
    var foundItems = 0;
    for (var i=0, j=oLinks.length; i<j; i++) {
      if ((sm.canPlayLink(oLinks[i]) || self.classContains(oLinks[i],self.playableClass)) && !self.classContains(oLinks[i],self.excludeClass)) {
        self.addClass(oLinks[i],self.css.sDefault); // add default CSS decoration
        self.links[foundItems] = (oLinks[i]);
        self.indexByURL[oLinks[i].href] = foundItems; // hack for indexing
        foundItems++;
      }
    }
    if (foundItems>0) {
      self.addEventHandler(document,'click',self.handleClick);
      if (self.config.autoPlay) {
        self.handleClick({target:self.links[0],preventDefault:function(){}});
      }
    }
    sm._writeDebug('inlinePlayer.init(): Found '+foundItems+' relevant items.');
  }

  this.init();

}

var inlinePlayer = null;

soundManager.setup({
  // disable or enable debug output
  debugMode: true,
  // use HTML5 audio for MP3/MP4, if available
  preferFlash: false,
  useFlashBlock: true,
  // path to directory containing SM2 SWF
  url: '../../swf/',
  // optional: enable MPEG-4/AAC support (requires flash 9)
  flashVersion: 9
});

// ----

soundManager.onready(function() {
  // soundManager.createSound() etc. may now be called
  inlinePlayer = new InlinePlayer();
});