Notes should have their opacity be equal to how high their velocity is.
This would both be helpful for people using the app to learn so that they can visually see how loud they're supposed to be playing, as well as making it look nicer visually, as parts that sound softer will also "look" softer.
Ideally, the notes should also have a thin outline around them that's always at 100% opacity so that they're still visible even at very low volume. This also makes the notes look very pretty aesthetically, as a bonus.
Here's an example mockup:
(The melody does a diminuendo and goes from as loud as possible at the bottom to as quiet as possible at the top. Obviously, this is a bit exaggerated just for the sake of demonstration, most diminuendos wouldn't be this extreme, but would just be somewhere in the middle)
Notes should have their opacity be equal to how high their velocity is.
This would both be helpful for people using the app to learn so that they can visually see how loud they're supposed to be playing, as well as making it look nicer visually, as parts that sound softer will also "look" softer.
Ideally, the notes should also have a thin outline around them that's always at 100% opacity so that they're still visible even at very low volume. This also makes the notes look very pretty aesthetically, as a bonus.
Here's an example mockup:
(The melody does a diminuendo and goes from as loud as possible at the bottom to as quiet as possible at the top. Obviously, this is a bit exaggerated just for the sake of demonstration, most diminuendos wouldn't be this extreme, but would just be somewhere in the middle)