as I mentioned before , this shield Has Inboard Keys to control the Audio file , and You can Control the Audio File by Programming from Arduino , You can program your Audio when it's begin , Switch between file and Control the Volume Up and Down very easy .
I want to Show you How we can Play Audio from SD Card and U Disk .
The component that we need is :
1) Arduino Board .
2) Arduino USB-SD MP3 Shield From ELECHOUSE You can buy it from here .
3) SD Card With adapter.Or USB Flash .
4) Speakers Or Headset .
Step 1: Arduino MP3 Shield
This Shield can controlled from Arduino By Hardware Serial "Rx D0 , Tx D1 " and By Software Serial " RX D7 , Tx D8" So at first You can Use Hardware serial , easy to use but you must remove the shield when you want to Upload new sketch .
You can change The Serial interface pin by solder tools , Just remove the solder from Upper 2 pads and solder a small bridge between the 2 pads below to active Software serial Pin . look to the image attached to see these 3 pads .
You can also Bridge amplifier control bridge so you can turn on or Off by solder Amplifier Control pin , so This pin attached to arduino D9 Pin , I didn't use it in this experiment
You can also Solder Pin header on This shield "Look at the Picture" So You can connect Speakers to this shield