src/main/java/org/intellimate/izou/sdk/frameworks/music/player/template/CommandHandler.java
public void setVolumeChangeableController(Consumer<Volume> controller) {
        if (controller == null)
            return;
        changeVolume = controller;
        capabilities.setChangeVolume(true);
    }
public void setVolumeChangeableController(Consumer<Volume> controller) {
        if (controller == null)
            return;
        changeVolume = controller;
        capabilities.setChangeVolume(true);
    }
adds the ability to change the volume from outside the player
@param controller  the controller for callback