diff --git a/doc/7-systems/ym2203.md b/doc/7-systems/ym2203.md
index 5a744db01..ccc39e8c4 100644
--- a/doc/7-systems/ym2203.md
+++ b/doc/7-systems/ym2203.md
@@ -107,8 +107,6 @@ several variants of this chip were released as well, with more features.
   - if `x` is `1` to `4`, the effect targets that operator; `y` turns it off with a value of `0` and on with a value of `1`.
     - for example, the effect `6031` enables OP3.
 - `61xx`: **set algorithm** (0 to 7).
-- `62xx`: **set LFO FM depth** (0 to 7).
-- `63xx`: **set LFO AM depth** (0 to 3).
 
 ## info