Yep, the music items are broken, there is currently no way to upload the file at this point. The only temporary solution for this is to put the music file, in .ogg format directly into your custom folder. Only you can hear it though, and if other people /dl you, they won't have your music.

BTW, when you put it into your custom folder, make it into a .ogg format. The reason for this is because when you upload it in .wav format, it gives better quality then converting it to .ogg. Toribash then converts the music into .ogg for compatability.