I have a 2015 GBP base model with standard audio. I have a USB with several general folders like BLUES,JAZZ,OLDIES,CLASSICAL,etc,etc. Within each of these general folders I have numerous folders by artists, and the mp3 files are within these folders.I can not find a way to select a general folder before anything else.The usb starts with the first general category and I dont see how to change to another category. TIA for any assistance, Turboman2015. Btw, the audio isnt as bad as some have stated, to me.