A few years ago myself and a friend wrote a simulator for a 90's toy called "Smart Start" ("Pense Bem" in Brazil), which has a crude piano (square wave only) mo

A few years ago myself and a friend wrote a simulator for a 90's toy called "Smart Start" ("Pense Bem" in Brazil), which has a crude piano (square wave only) mode as well. It is still online at http://labs.hardinfo.org/pb/ http://labs.hardinfo.org/pb/. To play, turn it on (green button), then press "Memória Tons" (third button from the right in the last row).