Wanted to say thanks for such a great looking player. I'd also like to add my suggestions too
1.) Multiple playlists
2.) Description text area should be moved to where you create a playlist
3.) Use a custom post type
4.) Browse button for uploading the mp3 file
To elaborate I think it would be very cool if this player used custom post types. The post type could be HTML5 Player for example. Instead of add new post, it would say add new playlist.
The WYSIWYG editor would be where you would enter the description of the album. Or instead of a WYSIWYG editor just a text area for the description. you could also have a section in this post type for adding the audio files with a browse button, want to add another audio file? Click the + to add another field with the browse button. Basically you can add each track for that album one at a time by uploading it right there vs copying the full URL path of the audio file.
The Featured Image could be the Album cover artwork. Another section of the post type could be for the Buy / Download button URL.
When you save the post (aka playlist) a shortcode is generated for that playlist, simply add that shortcode into posts or pages.
So many possibilities. Just my thoughts.
Still, a very nice player with tons of potential.