For my third and most likely final instrument of the project, I've been building a xylophone using piezo transducers for trigger detection. You may notice some plastic bongos in the back of this picture - I've been attempting to get Nintendo's 'DK bongos' to behave with an arduino but I've not had much luck yet.
The main circuit is pretty much wired up now - each of the 12 keys on the xylophone has a piezo transducer wired to an analog pin on an arduino mega. This allows for you to trigger notes of varying volume.
I also plan to use an ultrasonic sensor to alter the sound of the notes. I've tested this out on a breadboard earlier in this project as can be seen in this video:
It's worth mentioning that the 'bass' instrument is now complete as well as the pianocade I'll film a video soon.