### 2.2.71 Metronome_mark_engraver

Engrave metronome marking. This delegates the formatting work to the function in the `metronomeMarkFormatter` property. The mark is put over all staves. The staves are taken from the `stavesFound` property, which is maintained by Staff_collecting_engraver.

Music types accepted:

tempo-change-event

Properties (read)

> `currentCommandColumn` (graphical (layout) object)

>   Grob that is X-parent to all current breakable (clef, key signature, etc.) items.

> `currentMusicalColumn` (graphical (layout) object)

>   Grob that is X-parent to all non-breakable items (note heads, lyrics, etc.).

> `metronomeMarkFormatter` (procedure)

>   How to produce a metronome markup. Called with two arguments: a `TempoChangeEvent` and context.

> `stavesFound` (list of grobs)

>   A list of all staff-symbols found.

> `tempoHideNote` (boolean)

>   Hide the note = count in tempo marks.

This engraver creates the following layout object(s):

MetronomeMark.

`Metronome_mark_engraver` is part of the following context(s): Score.

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