How it works
A play note block makes a sound. A note has two things: how high or low, and how long.
Pitch is how high or low a note sounds. Length is how long it rings, counted in beats, from one beat for short to four for long.
A rest is a pause, so it makes no sound. A repeat block plays a tune again, with no copying blocks.
Four of the same note just beep, so change the pitch and the length to make a tune.