Found in documentation two years 80, this toy instrument uses an integrated circuit little commonly. As notes are given the values of key series resistors on the keyboard.
This UAA170 application circuit was taken from Siemens' own integrated circuits manual from 1976....
The astable multivibrator shown by the figure can produce signals in the 10 to 10 000 Hz band...
Found in an American publication from the 1980s, this circuit can be found in commercial sound...