Edit in JSFiddle

var holding = false;
var track = document.getElementById('track');
var progress = document.getElementById('progress');
var play = document.getElementById('play');
var next = document.getElementById('next');
var prev = document.getElementById('prev');
var title = document.getElementById('title');
var artist = document.getElementById('artist');
var art = document.getElementById('art');
var current_track = 0;
var song, audio, duration;
var playing = false;
var songs = [{
    title: 'Mother\'s Day',
    artist: 'Offspring Fling',
    url: 'http://abarcarodriguez.com/365/files/offspring.mp3',
    art: 'http://abarcarodriguez.com/365/files/offspring.jpg'
},
    
{
    title: 'Blackout City',
    artist: 'Anamanaguchi',
    url: 'http://abarcarodriguez.com/365/files/anamanaguchi.mp3',
    art: 'http://abarcarodriguez.com/365/files/anamanaguchi.jpg'
},

{
    title: 'The Primordial Booze',
    artist: 'Rainbowdragoneyes',
    url: 'http://abarcarodriguez.com/365/files/rainbow.mp3',
    art: 'http://abarcarodriguez.com/365/files/rainbow.jpg'
}];

window.addEventListener('load', init(), false);

function init() {
    song = songs[current_track];
    audio = new Audio();
    audio.src = song.url;
    title.textContent = song.title;
    artist.textContent = song.artist;
    art.src = song.art;
}


audio.addEventListener('timeupdate', updateTrack, false);
audio.addEventListener('loadedmetadata', function () {
    duration = this.duration;
}, false);
window.onmousemove = function (e) {
    e.preventDefault();
    if (holding) seekTrack(e);
}
window.onmouseup = function (e) {
    holding = false;
    console.log(holding);
}
track.onmousedown = function (e) {
    holding = true;
    seekTrack(e);
    console.log(holding);
}
play.onclick = function () {
    playing ? audio.pause() : audio.play();
}
audio.addEventListener("pause", function () {
    play.innerHTML = '<img class="pad" src="http://abarcarodriguez.com/lab/play.png" />';
    playing = false;
}, false);

audio.addEventListener("playing", function () {
    play.innerHTML = '<img src="http://abarcarodriguez.com/lab/pause.png" />';
    playing = true;
}, false);
next.addEventListener("click", nextTrack, false);
prev.addEventListener("click", prevTrack, false);


function updateTrack() {
    curtime = audio.currentTime;
    percent = Math.round((curtime * 100) / duration);
    progress.style.width = percent + '%';
    handler.style.left = percent + '%';
}

function seekTrack(e) {
    event = e || window.event;
    var x = e.pageX - player.offsetLeft - track.offsetLeft;
    percent = Math.round((x * 100) / track.offsetWidth);
    if (percent > 100) percent = 100;
    if (percent < 0) percent = 0;
    progress.style.width = percent + '%';
    handler.style.left = percent + '%';
    audio.play();
    audio.currentTime = (percent * duration) / 100
}
function nextTrack() {
    current_track++;
    current_track = current_track % (songs.length);
    song = songs[current_track];
    audio.src = song.url;
    audio.onloadeddata = function() {
      updateInfo();
    }
}

function prevTrack() {
    current_track--;
    current_track = (current_track == -1 ? (songs.length - 1) : current_track);
    song = songs[current_track];
    audio.src = song.url;
    audio.onloadeddata = function() {
      updateInfo();
    }
}

function updateInfo() {
    title.textContent = song.title;
    artist.textContent = song.artist;
    art.src = song.art;
    art.onload = function() {
        audio.play();
    }
}
<div id="player">
    <img src="" class="cover" id="art" />
    <div class="trackinfo">
        <p id="title"></p>
        <p id="artist"></p>
    </div>
    <div id="track">
        <div id="progress"></div>
        <div id="handler"></div>
    </div>
    <div class="container">
        <div class="info">
            <div class="cont">
                <button id="prev" class="nav">
                    <img src="http://abarcarodriguez.com/lab/prev.png" />
                </button>
                <button id="play" class="nav">
                    <img class="pad" src="http://abarcarodriguez.com/lab/play.png" />
                </button>
                <button id="next" class="nav">
                    <img src="http://abarcarodriguez.com/lab/next.png" />
                </button>
            </div>
        </div>
    </div>
</div>
* {
    margin: 0;
    padding: 0;
}
body {
    background-color: #F4F4F4;
    font-family:'Helvetica';
}
#player {
    width: 400px;
    height: 400px;
    position: absolute;
    top: 50%; left: 50%;
    margin-left: -200px;
    margin-top: -200px;
    border-radius: 50%;
    border: 1px solid #D0D0D0;
}
#player .cover {
    width: 400px;
    position: absolute;
    top: 0;
    left:0;
    border-radius: 50%;
}
#player .container {
    width: 100%;
    height: 100%;
    border-radius: 50%;
    position: absolute;
    top: 0;
    left: 0;
    overflow: hidden;
}
#player .info {
    position: absolute;
    bottom: 0;
    left: 0;
    width: 400px;
    height: 115px;
    background-color: #FFF;
}
#player .info .cont {
    text-align: center;
    padding-top: 25px;
}
#player .trackinfo {
    position: absolute;
    bottom: 135px;
    color: #FFF;
}
#player .trackinfo p {
    text-shadow: 0px 0px 5px #333;
}
#player .trackinfo #title {
    font-weight: bold;
    font-size: 30px;
    padding-left: 10px;
    margin-bottom: 5px;
}
#player .trackinfo #artist {
    padding-left: 25px;
}
#track {
    width: 366px;
    height: 5px;
    position: absolute;
    background-color: #A6A7A9;
    bottom: 115px;
    left: 17px;
    z-index: 10;
    cursor: pointer;
}
#progress {
    float: left;
    height: 5px;
    width: 0%;
    background: #00CC99;
    cursor: pointer;
}
#handler {
    position: absolute;
    width: 20px;
    height: 20px;
    background-color: #00CC99;
    top: 50%;
    left: 0%;
    margin-left: -10px;
    margin-top: -10px;
    border-radius: 50%;
    cursor: pointer;
    z-index: 5;
}
.nav {
    width: 50px;
    height: 50px;
    vertical-align: top;
    background-color: #FFF;
    border: 2px solid #00CC99;
    border-radius: 50%;
    outline: none;
    margin: 0 7px;
    cursor: pointer;
}
.nav:hover {
    background-color: #00CC99;
}
.nav img {
    height: 20px;
    vertical-align: middle;
}
.pad {
    padding-left: 5px;
}
#prev {
    padding-right: 5px;
}
#next {
    padding-left: 4px;
}