The key cup of a covered key (also knows as "German style" or "plateau style") does not require the player to cover a hole with their fingers. The key covers the tone hole to prevent air from escaping. In contrast, the key cup of a ring key has a hole than the player must cover with their finger. While it takes some training to be able to accurately and consistently press on the tone hole with ring keys, you can directly feel the air vibrations through your fingers. This means you can produce finely nuanced sounds. With ring keys, it is even possible for advanced players to control their intonation by changing how their fingers cover the tone holes.
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