diff --git a/doc/2-interface/menu-bar.md b/doc/2-interface/menu-bar.md
index 9a5c2d17b..fee8f7c57 100644
--- a/doc/2-interface/menu-bar.md
+++ b/doc/2-interface/menu-bar.md
@@ -122,6 +122,7 @@ the following settings are available:
   - I suggest you use the same rate as the song's.
   - apparently ZSM doesn't support changing the rate mid-song.
 - **loop**: enables loop. if disabled, the song won't loop.
+- **optimize size**: removes unnecessary commands to reduce size.
 
 click on **Begin Export** to... you know.
 
diff --git a/doc/2-interface/settings.md b/doc/2-interface/settings.md
index c7f01e8ff..8b6da2a00 100644
--- a/doc/2-interface/settings.md
+++ b/doc/2-interface/settings.md
@@ -49,7 +49,6 @@ settings are saved when clicking the **OK** button at the bottom of the dialog.
 - **When creating new song**:
   - **Display system preset selector**
   - **Start with initial system**
-- **Restart song when changing chip properties**
 
 ### Start-up
 
diff --git a/doc/7-systems/opll.md b/doc/7-systems/opll.md
index 92a81490b..f32f1eefc 100644
--- a/doc/7-systems/opll.md
+++ b/doc/7-systems/opll.md
@@ -13,10 +13,8 @@ the YM2413 is equipped with the following features:
 
 - 9 channels of 2 operator FM synthesis
 - a drum/percussion mode, replacing the last 3 voices with 5 rhythm channels, with drum mode tones hard-defined in the chip itself, like FM instruments. only pitch might be altered.
-
   - drum mode works like following: FM channel 7 is for Kick Drum, which is a normal FM channel but routed through mixer twice for 2× volume, like all drum sounds. FM channel 8 splits to Snare, Drum, and Hi-Hat. Snare Drum is the carrier and it works with a special 1 bit noise generator combined with a square wave, all possible by overriding phase-generator with some different synthesis method. Hi-Hat is the modulator and it works with the noise generator and also the special synthesis. CH9 splits to Top-Cymbal and Tom-Tom, Top-Cymbal is the carrier and only has the special synthesis, while Tom-Tom is basically a 1op wave. 
   - special synthesis mentioned already is: 5 square waves are gathered from 4×, 64× and 128× the pitch of channel 8 and 16× and 64× the pitch of channel 9 and they go through a process where 2 HH bits OR'd together, then 1 HH and 1 TC bit OR'd, then the two TC bits OR'd together, and those 3 results get XOR'd.
- 
 - 1 user-definable patch (this patch can be changed throughout the course of the song)
 - 15 pre-defined patches which can all be used at the same time
 - support for ADSR on both the modulator and the carrier
@@ -37,7 +35,7 @@ the YM2413 is equipped with the following features:
   - `y` is the multiplier.
 - `18xx`: **toggle drums mode.**
   - `0` disables it and `1` enables it.
-  - only in drums chip.
+  - only in drums mode.
 - `19xx`: **set attack of all operators.**
 - `1Axx`: **set attack of operator 1.**
 - `1Bxx`: **set attack of operator 2.**
@@ -69,3 +67,8 @@ the YM2413 is equipped with the following features:
 # info
 
 this chip uses the [FM (OPLL)](../4-instrument/fm-opll.md) instrument editor.
+
+## chip options
+
+- **Ignore top/hi-hat frequency changes**: in drums mode, makes the top/hi-hat channels not write frequency since they share it with snare and tom
+- **Apply fixed frequency to all drums at once**: sets the frequency of all drums to that of a fixed frequency OPLL drums instrument when one note with it is reached
diff --git a/doc/README.md b/doc/README.md
index 90e6e905b..bc09ca623 100644
--- a/doc/README.md
+++ b/doc/README.md
@@ -12,6 +12,8 @@ this documentation is a work in progress! expect several sections to be incomple
 8. [advanced topics](8-advanced/README.md)
 9. [guides](9-guides/README.md)
 
+online documentation may reflect developments newer than the current release.
+
 # attribution
 
 writers: