We cannot verify that all 3rd party music apps will work seamlessly with Vi at this point. It is a known music experience issue that Vi likes to push out her Spotify or local music audio whenever a run is started despite having another music app playing in the background. This is something we are working on fixing. Currently some 3rd party apps work better than others due to how they have configured their sharing services to other apps. You can try to play music from other apps with these steps:
1. Open up your third party app and start playing your music, podcast, audiobook, etc.
2. Open the Vi app and start your run.
3. When the music in Vi starts playing, pause it.
4. Click play on your third party app.
In the future we plan to have most of the popular music streaming services work seamlessly with Vi.