The project is a little trumpet practice instrument. Here's a little video of the finished project and the circuit:
The device plays tones through a speaker to match the frequency of the notes played on an actual trumpet using the same fingering.
One button is the "mouthpiece", the embouchure reading determines how high the note will be, the three valve buttons determine which fingering is applied.
The trumpet goes to sleep after 5 minutes to save the battery.
The fingerings are based off of this list: https://bobgillis.wordpress.com/2012/08/24/bb-trumpet-fingering-chart-and-overtone-series/