These accidentals were not actually proposed by Richard Stein or Bernd
Zimmermann, but are instead logical extensions of their symbols adding
arrows to provide options for notating slight pitch modifications[^1].

[^1]: Gould, *ibid.*, page 96 acknowledges the Stein-Zimmermann accidentals as the most commonly-used symbols with fixed meanings; however, the extensions provided here do not have fixed meanings.
