Closed hole

A filled hole in a wind-instrument fingering diagram means that the indicated tone hole or key is fully closed. It describes fingering, not a notehead or articulation.

Closed hole: music notation symbol placed above the note. Cover the hole completely.
Family
Wind and brass signs
Where it sits
Above the note
What it looks like
A circle

Do not confuse it with

An empty hole is open; a half-filled hole is only partly covered.

What the sources say

All notation signs

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