In this chapter, we will build a configurable MIDI-controlled xylophone-like instrument made with empty glass bottles and a set of servos. This will make use of almost all of the Pi's GPIO headers to drive the servos.

The servos are controlled using a web application that allows you to upload a MIDI file, set a temp, and allows the Pi to play the file on the bottles using a configuration file to tell it which bottle is tuned to which note. The tuning itself is done by varying the level of water in each bottle.

Since this project requires a lot of GPIO pins, you may wish to opt for a B+ model, which has an additional nine GPIO pins on its 40-pin connector.