The ringtone text transfer language (RTTTL) is a way to represent music data for play on older mobile phones. The format was created by Nokia for thier phones, but it also works with GPIO pins and a piezo buzzer.
This project shows how to use the Raspberry Pi's GPIO pins to play RTTTL on a piezo buzzer. This project was inspired by existing RTTTL implementations, but differs from those in that its user interface is Web enabled.
The application, written in Java, starts an HTTP server. The HTTP server presents the user interface via HTML. The user interface provides a list of built-in RTTTL ditties available for play. The application's interface also accepts user-provided RTTTL sequences, via its on-the-fly input controls.