sound on Win/PC and Android/Tablet

[onitima]

Enable FTP and use apps login. There you will see user directory where files that can be accessed from HTTP /user/ path should be placed.

Thanks, admin! This clarified sufficiently to solve the problem. For the benefit of any future visitors to this post:

The file /user/audio1.mp3 should be under the home ftp folder of user 'apps' (on the visualisation server).  In my case, the first FTP client I used did not show the contents of my home ftp folder. But the second client which I tried (due to a hunch) did.