I used to run a oxwall site for Australian hiphop and this feature would have been so useful back then now i dont run the site so the need is not there, however im sure this is something people would like to see. only prob with uploading music is Legal, it's quite costly to get a licence to have streaming music on your website.

without such you will run into a number of issues and even possible lawsuits, pretty sure each country has it's own licencing, tho i'm not 100% sure. it's something you will need to fully understand before you even bother about making plugins or adding features like this.

However if your suggesting adding streaming music from sites like soundcloud and stuff then you should be fine, or even free music. but lets face it who wants to hear songs we have never heard before if your wanting awesome music you want what we all hear on the radio or out in nightclubs and for that you will need quite costly licencing. 

Even if your intentions where to have free music or even legal music uploads the amount of time you will spend monitoring the uploads will be crazy - T's an C's on saying stuff like your responsible for your own uploads wont save you for long. you will have more DMCA claims filed against your site than you will be able to deal with not to mention what thats going to look like in google search, lol people will look for your site and see more illegal activity than legal before too long if that feature was used alot.

there are a few sites that could use this tho after saying all that, if your trying to build a site like reverbnation and soundcloud, These sites work by allowing music artist to upload there own music they have personally created then that's where this plugin would be so useful. 

Here is the plugin you are looking for: Audio plugin