diff --git a/papers/doc/7-systems/ym2151.md b/papers/doc/7-systems/ym2151.md
index 60764d193..fc297f2ee 100644
--- a/papers/doc/7-systems/ym2151.md
+++ b/papers/doc/7-systems/ym2151.md
@@ -28,6 +28,8 @@ in most arcade boards the chip was used in combination with a PCM chip, like [Se
 - `1Bxx`: set attack of operator 2.
 - `1Cxx`: set attack of operator 3.
 - `1Dxx`: set attack of operator 4.
+- `1Exx`: set LFO AM depth.
+- `1Fxx`: set LFO PM depth.
 - `30xx`: enable envelope hard reset.
   - this works by inserting a quick release and tiny delay before a new note.
 - `50xy`: set AM of operator.