Poor man's AVR music box

Step 4 Song storage code explained

It works like this:

control:
Start timer
Wait for timer overflow
Loop a certain number of times (this is the note length)
increment note number

Song data:
is the note number =1?
if so, output the correct number out port A, PIN0, and load the note length into a register
if not, continue

is the note number=2?
...
...
ad nauseum, over 300 notes
...
...
is the song finished?
if yes, clear all registers
if not, return to the "wait for timer overflow" step, with the correct note length value in the appropriate register. It will then increment note number and return to the "song data" function.