### 1.1.33 KeyChangeEvent

Change the key signature.

Syntax: `\key` name scale

Event classes: key-change-event, music-event and StreamEvent.

Accepted by: Key_engraver and Key_performer.

Properties:

> `name` (symbol):

>   `'KeyChangeEvent`

>   Name of this music object.

> `to-relative-callback` (procedure):

>   `#<procedure #f (x p)>`

>   How to transform a piece of music to relative pitches.

> `types` (list):

>   `'(general-music key-change-event event)`

>   The types of this music object; determines by what engraver this music expression is processed.

#### Internals Reference v2.18.2 (稳定分支).