alda-mirror/doc/markers.md

Markers

Markers can be placed and referenced at any point during a score, and in any instrument part. e.g. %chorus will place a marker called "chorus" at the current offset, and then using @chorus at any point will set the current offset to that of the "chorus" marker.

A marker cannot be referenced before it is placed -- for example, the following score will result in an error:

piano:
  @someMarkerThatDoesntExistYet
  c8 d e f g2

guitar:
  r1
  %someMarkerThatDoesntExistYet

Instead, the placement of the marker must occur before the marker is referenced:

guitar:
  r1
  %existingMarker

piano:
  @existingMarker
  c8 d e f g2

Acceptable Marker Names

Marker names follow the same rules as instrument names.