LilyPond Internals Reference: 2.2.56 Keep_alive_together_engraver

### 2.2.56 Keep_alive_together_engraver

This engraver collects all `Hara_kiri_group_spanner`s that are created in contexts at or below its own. These spanners are then tied together so that one will be removed only if all are removed. For example, if a `StaffGroup` uses this engraver, then the staves in the group will all be visible as long as there is a note in at least one of them.

`Keep_alive_together_engraver` is part of the following context(s): PianoStaff.

#### Internals Reference