If your post contains audio, then you should use this post format. Select Audio in the appeared metabox and add link to your mp3 file. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. In faucibus, risus eu volutpat pellentesque, massa felis feugiat velit, nec mattis felis elit a eros. Cras convallis sodales orci, et pretium sapien egestas quis. Donec tellus leo, scelerisque in facilisis a, laoreet vel quam. Suspendisse arcu nisl, tincidunt a vulputate ac, feugiat vitae...