This XF2 add-on along with the entire collection can be purchased for $35.00 USD. Your Premium upgrade will allow you to download as many XF2 add-ons as you like for one year. Please see the entire collection located in the Resources area at this URL:
Opens MP3 attachments in the browser.
By default XenForo requires MP3 attachments to be downloaded before you can listen to them. This add-on changes this default behavior so that MP3 attachments open directly in the browser when they are clicked.
(Example of MP3 attachment)