This will be a big one... guests should be able to view your list on multiple devices (probably their phones), and then somehow request a song which will then get added to a central host playlist. The host account/device should show the selected songs and sort them by number of requests, time of request, and/or other relevant factors.
A host should have the ability to
- Indicate whether guests can see the full track list, owned+wanted songs, or just owned songs.
- Remove songs from the playlist and/or mark songs as "played"
- Clear the entire playlist