In WonderPlugin Audio Player, step 1, add your mp3 files, then in step 2 Skins dialog, select a bar skin, for example, Bar, "White Bar", "Bar with Title" or "White Bar with Title".
Step 2 - Customise the player
1. In the plugin, step 3 Options tab, Advanced Options, enter the following text to the Custom CSS input box:
3. In step 3 Options tab, Skin Options, add 100 to the option width. This will give some extra space for the download link. For example, if you have selected the skin "Bar", the default width is 300, you can change the value to 400.