[vintermann]

It really isn't. You highlight something important: musicians don't usually learn to convert notation to music in their heads. Instead, they learn to associate notation with how to make the sound, e.g. finger positions.

I remember in ear training class in high school all the brass kids playing imaginary valves with their fingers when trying to sight-sing.

It's harder for singers, and quadratically harder for instruments where you have more positions and play more notes at once.

[InitialLastName]

It seems like there's a three-way connection that forms in a musician's head between the note on the page, the sound the note makes, and the muscle memory for playing the note. Each connection is strengthened by different types of practice, and supported by each other, but often with the way we teach music the kinetic is a proxy between the aural and the visual; this is especially true of people who learn mechanical instruments.

One way to boost the aural/visual connection (when you already have strong aural/kinetic and visual/kinetic connections) is to pick up instruments that are very different from the ones you already know; I would think this is the goal of music education programs requiring basic proficiency with piano and singing, regardless of the student's main instrument. Once you have to learn a new set of muscle memory associations to go from the same note on the page to the same note in your ear, it starts to break down the strength of the muscle memory associations.

[scrozier]

However, if you can sight sing, it makes playing music on a wind instrument much easier, as you have a target in your head for what the note should sound like as you play it. Sight singing is a very good skill for instrumentalists.