You can only use this app if you have a Makey Makey. if you have a PlayStation 4/5 or something, and you have a Makey Makey plugged into it and the Piano app on the website doesn’t work on PlayStation or something and you can get on scratch then try this
Credits to Makey Makey for some sounds if you want to see the real app go to the link or copy it https://apps.makeymakey.com/piano/
