Execute the program at 0D00, and then type keys, different keys will result in different notes.

I prefer to program in Basic, so how do we use Basic to work the PIO. Answer, read the manual and you will find that

OUT 6,15

sets the PIO to the output mode, note that 15 is the decimal of 0FH. To output from the PIO in Basic, use

OUT 4,A

where A is a decimal value between 0 and 255. We can now write a program to play a simple tune, in the following example I used the machine code program to find the notes, converting the character displayed to decimal, and then putting the number into the data. Happy tune playing.

National Anthem

Option to give a mandolin effect insert the following

M. L. Trim