Most people either use #tunestr or #nowplaying. Technically, it'd be possible to just listen on many relays for messages involving this particular tag. But noone has written that ... yet. ;)
Discussion
I was thinking more automated, and not necessarily something that shows up in the feed. More like how last.fm works for music, or trakt.tv for movies and tv. Eventually these events could create a history of what you had listened to and watched. It would be neat to have my music listening history as part of my Nostr identity.