Minecraft wiki entry for Redstone_music, associated text: C: Right-click note block 6 times
D: Right-click note block 8 times
E: Right-click note block 10 times
F: Right-click note block 11 times
G: Right-click note block 13 times
A: Right-click note block 15 times.
Quarter note (exclusively "Twinkle Twinkle Little Star"): 4 tick repeater + 2 tick repeater (6 redstone ticks)
Half note (exclusively "Twinkle Twinkle Little Star"): 4 tick repeater + 4 tick repeater + 4 tick repeater (12 redstone ticks)