This tool (and writing it) helped me to understand how music functions.
I have put this little project under GPL so maybe others can profit from it or have some fun. The metronome is especially usefull to play with and maybe learn about the length of notes. I find it kind of hypnotizing looking at the piano playing, or listening to freshly invented rhythms.
Java programmers can here find a few useful examples on how to use MIDI in Java - I did not find much (understandable) about it on the web when I wrote this GUI in 2009.
Many thanks to Wei in Tuebingen (Snowmans Dream) who showed me to play the piano in just two days back in 2009 - without I would have never started this -, many thanks to the project creators of the Gervill project - without their work I would have stopped in the beginning because the default Java Soundbanks sound is so weak, and of course many thanks to those who put their MIDI files online for everybody; I have packed some of them into the current distribution.
(Despite of the long ToDo list at the moment I have no intention to continue this project.)