We called it the PA. Back in the day when I was involved in organising and setting up parties and small concerts. (each about once a year). Not very accurate (looked it up just now) , but you might hear it referred to as such.
We’ve even been doing that for thousands of years!
This might turn in to something worthwhile: https://smallandroidphone.com/
I’m here just to join you shouting out. Great peace of software.