I would love to have the possibility to add a song to an activity that I listened to during my workout. For example, when I go running, there is often one specific song that motivates me the most or becomes part of the memory of that activity. At the moment, I can only mention it in the text description, but it would be amazing if friends on Strava could directly listen to the song as part of the post itself.
I imagine it working similarly to the music feature on Instagram Posts, where music adds emotion and personality to shared moments.