<audio src="track1.mp3" controls></audio>
<audio src="track2.mp3" controls></audio>
<audio src="track3.mp3" controls></audio>
<audio src="track4.mp3" controls></audio>
<audio controls>
<source src="track1.ogg">
<source src="track1.mp3">
</audio>
<audio controls>
<source src="track2.ogg">
<source src="track2.mp3">
</audio>