The best way to make Apple Music louder on Bluetooth is by adjusting the volume controls on your Bluetooth as well as the device you are using to play the music. If it is your iPhone or an iPad, ensure your volume is at the level you want by using the volume buttons on the side of your device. If you are using a Mac, remember that your volume controls can be found in the menu bar by clicking the speaker icon or hamburger icon for Control Center. You can also try adjusting your EQ settings following the steps above.