We’re terribly sorry to hear about your loss. We'll do our best to help you with your question.
In general, this is something that your phone manufacturer can answer with certainty, but as far as we're aware, it's not possible to prevent incoming/outgoing calls from interrupting the playback, as those take priority over everything else that's running on your phone at that moment.
With this in mind (and if Bluetooth is the only way to connect to the sound system at the venue), it's best to use a second dedicated device for the Spotify playlist, making sure to disable all notifications and incoming calls and downloading the playlist for offline listening in case of any connectivity issues. Using the Connect feature, you'll also be able to control the playlist from your primary device (if needed).
If however the sound system supports Spotify Connect and you have the option to connect your phone to the venue's WiFi network, you'll be able to use your phone without any issues, since the sound system will act as a standalone streaming device and won't be dependent on your phone's audio output.
We hope this helps. Don't hesitate to ask if you have any further questions.
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