Using an Arduino UNO board I built a drummer that can play musical notes on a Xylophone-like arrangement, which is controlled by a phone app (Android) via a Bluetooth connection. The phone app was developed using App Inventor 2 (ai2.appinventor.mit.edu/).
I fixed one servo on top of another like in the image above, and then using some plastic trunking I fixed the assembly on a piece of wood board. Using a metal wire, some blu-tack and a bolt I built the drumming arm, which I finally glued to the servo arm. You will also need to glue the Xylophone "notes" around this arm, and adjust the angles in the Arduino sketch in order for the arm to hit the desired notes.
One XBee Bluetooth shield and one XBee Bluetooth module are required in order to connect the Arduino to the phone app and send drumming instructions.
The LEDs are for visual effect only, and are not absolutely required for this project to work. Follow the schematic for connecting all the components - additional info to be found in the Arduino sketch (drummer.ino)
You can download the ready-made phone app (APK file; tested on my Samsung Galaxy S2 - I know, it's an old phone :-) ), or the App Inventor 2 project, if you wish to make any changes yourself (.AIA file; you will need to register an account with ai2.appinventor.mit.edu/ in order to be able to do this).