This will not work with Arduino IDE 1.6.5 (or below) or with non ESP32-S2/S3 devices (e.g. Arduino UNO, Arduino MEGA, etc.). To use this library you need to have Arduino core for the ESP32 installed.
This library supports both BK3254 and BK3266 based Bluetooth audio modules. These modules communicate using "ASCII" mode commands (AT+, COM+, BT+, FM+ prefixes). BK3254: Original module, uses AT ...