a keyed instrument的用法和样例：
- To bring about this change, price mechanisms were a key instrument.
- a keyed instrument; the locks have not yet been keyed.
- As he picked up the envelope, a key dropped out.
- As she picked up the envelope, a key dropped out.
- A key of an instrument, such as a piano.
- A slot for a key in the hub or shaft of a wheel.