GitHub

This guide will help you mirror your mobile phone screen on your desktop using ADB (Android Debug Bridge) and scrcpy. Follow the steps below to set up and run the tools.

Android device with Developer Options enabled. USB cable to connect your phone to your desktop. A computer running Windows with ADB and scrcpy installed.
GitHub

Audio Share can share Windows/Linux computer's audio to Android phone over network, so your phone becomes the speaker of computer. (You needn't buy a new speaker .)

The audio player on PC can work normally. That's to say that you should have a sound card and the audio endpoint is in available state. Otherwise, you need some extra setups. Android 6.0(API 23)+.