It's unlikely people you'd be able to trick people into thinking the note was handwritten but hopefully the robot will give you some ideas on how to do this sort of thing.
As erco mentioned in the video, he used a Basic Stamp 2 to control the servos.
thanks, are there any tutorials on how to develop this
Can you move a servo? Can you move a stepper? If no to either question, then you are not ready to make the machine do anything.
If yes to both questions, then all you need to do is define an implement a means of defining how the servoand steppers are to move and the timing between the moves. It's really no different from driving a CNC machine.
Some program that knows what a font looks like as a series of vectors converts the text to write to a series of M and G codes to drive the CNC machine and sends the data to the Arduino that is responsible for nothing more than moving the servo and steppers.