I see, I'm still not sure exactly how you wanna make it work, for example, you upload a song but what happens after? do just save it in a general list? or do you link that song with a specific button? etc... there are many questions that only you know so generally answers will change according to each situation.
At the moment I can only assume what are you trying to do:
1-It looks like you select one of those 10 buttons
2-Then you press that upload button then when the song is uploaded you link that song to that button?
If that is correct here is an example:
https://www.dropbox.com/s/7ah5attx9u9e9ve/Upload%20song1.capx?dl=0
And if you need instead to upload to a general list instead of binding it to a button then the link I posted above has an example of how to do that, hopefully will help you any of those two examples.