Changing Save As Filename - Page Which Allows Access To Music On A Server ?

I am currently developing a page which allows access to music on a server. This music is being streamed, but users are also able to download this music (assuming they have the license to do so). All of the music uploaded is of the .mp3 format, however they have no filetype extensions, and were not named using any particular naming convention. Because of this, I was hoping to change the filename (when a downloaded is initiated) to variables I have stored based on the current song.

I am currently simply opening a new page, in Chrome is looks like this: chrome.tabs.create({ "url": song.url })

Hit presents the user with a prompt to save the file, however, its default name is a random alphanumeric string with no extension, as per their file name on my server. Is there an easy way to do this without renaming all the music server side? I do have the variables song.title and song.artist setup!

Edit: Since this page is only for Chrome users, I listed the code I am using. I understand window.open and was originally using this. It functions the same, and if I need to revert back to using is instead, I shall.