The Arduino Built-in Example "02.Digital / toneKeyboard" (documented at https://www.arduino.cc/en/Tutorial/BuiltInExamples/toneKeyboard) requires three force-sensing resistors. Such force-sensing resistors are usually not included in starter kits, and they are relatively expensive to buy separately.
I've modified the project to use three capacitive sensors instead. Anyone can download the files for this modified project here: https://drive.google.com/file/d/11gkXddfvVPVloyt3IDVSYYqXZ8USX6Zu/view?usp=sharing