Does Gamepadpiano work on a steamdeck?

Yes it does, you need to download and unzip the Linux x86 64bit version somehere on the steam deck.
Do this in desktop mode and give execution permissions to the downloaded and unzipped gamepadPiano.x86_64 file.
This will be asked when pressing that file.
Right click on the file, or long press and choose "Add to steam".
Return to Gaming mode with the shortcut on the desktop.
gamepadPiano.x86_64 is now added to NON-STEAM games and can be used to create music on your device.

Tip: use Arpeggiator as drum computer

Playing drums may not be as fun as playing melodies with gamepadpiano, but you can choose one of the drum kits as your instrument: "House","Industrial","Chaos CM-64/32 Drum","Chaos Kick&Snare Drum" and set is an an arp in the Settings overlay or with mouse or touch in the Main screen.

When the instrument is set as arpeggiator, note(s) that are being pressed will play in a cycle, one by one in a set speed, determined by the bpm and set arp speed, which creates a fixed rhythm.

Resetting settings

Settings are being saved in a config file "" wich is a json file.
This file is always saved in the default save location wich is the user data folder of godot.
That is the user directory of your system in the following folders:

  • Windows:AppData/Roaming/Godot/ app_userdata/Gamepad Piano
    In explorer the Appdata path can be found by entering %APPDATA%
  • MacOS: ~/Library/Application Support/Godot/app_userdata/Gamepad Piano
  • Linux: .local/share/godot/app_userdata/Gamepad Piano

In the setting there is is a Save location. The default save location is shown here, when it is not changed by the user.
save location in settings

It is possible, but not recommended, to change content of this file.
Only Gamepad Piano should change this file.
When something goes wrong however, you can just delete this file and a new one will be created with default values when the application is started.
For android that location may not be accessible trough other applications. Removing and reinstalling the application will reset the config file to defaults.