diff --git a/doc/5-wave/README.md b/doc/5-wave/README.md
index 19a07b104..a42ffd815 100644
--- a/doc/5-wave/README.md
+++ b/doc/5-wave/README.md
@@ -6,7 +6,11 @@ Furnace's wavetable editor is rather simple, you can draw the waveform using mou
 
 Furnace's wavetable editor features multiple ways of creating desired waveform shape:
 
-- Shape tab allows you to select a few predefined basic shapes and indirectly edit it via "Duty", "Exponent" and "XOR Point" sliders TODO: what the last two are doing? What is amplitude/phase for?)
+- Shape tab allows you to select a few predefined basic shapes and indirectly edit it via "Duty", "Exponent" and "XOR Point" sliders:
+  - `Duty` slider affects mainly pulse waves, determining its wisth, like on C64/VRC6
+  - `Exponent` powers the waveform in the mathematical sense of the word (^2, ^3 and so on)
+  - `XOR Point` determines the point where the waveform gets negated.
+  - TODO: amplitude/phase part
 - FM is for creating the waveform with frequency modulation synthesis principles: One can set carrier/modulation levels, frquency multiplier, connection between operators and FM waveforms of these operators.
 - WaveTools allows user to fine-tune the waveform: scale said waveform in both X and Y axes, smoothen, amplify, normalize, convert to signed/unisgned, invert or even randomize the wavetable.
 
diff --git a/doc/6-sample/README.md b/doc/6-sample/README.md
index 05891a49a..2f4fe3cd4 100644
--- a/doc/6-sample/README.md
+++ b/doc/6-sample/README.md
@@ -1,6 +1,6 @@
 # samples
 
-In the context of Furnace, a sound sample (usually just referred to as a sample) is a string of numbers that hold sampled PCM audio.
+In the context of Furnace, a sound sample (usually just referred to as a sample) is a string of numbers that represent sampled PCM audio.
 
 In Furnace, these samples can be generated by importing a .wav (think of it as an higher quality MP3) file.
 
@@ -13,6 +13,7 @@ as of Furnace 0.6, the following sound chips have sample support:
 - PC Engine/TurboGrafx-16/HuC6280
 - Amiga/Paula
 - SegaPCM
+- NEC PC-9801/YM2608 (ADPCM channel only)
 - Neo Geo/Neo Geo CD/YM2610 (ADPCM channels only)
 - Seta/Allumer X1-010
 - Atari Lynx
@@ -21,12 +22,16 @@ as of Furnace 0.6, the following sound chips have sample support:
 - QSound
 - ZX Spectrum 48k (1-bit)
 - RF5C68
-- WonderSwan
+- SNES/S-DSP
+- WonderSwan (second channel only)
 - tildearrow Sound Unit
 - VERA (last channel only)
 - Y8950 (last channel only)
 - Konami K007232
-- a few more that I've forgotten to mention
+- Irem GA20
+- Ensoniq OTTO/ES5506
+- Yamaha PCMD8/YMZ280B
+- MMC5 (last channel only)
 
 ## compatible sample mode
 
@@ -45,9 +50,9 @@ due to limitations in some of those sound chips, some restrictions exist:
 - NES: if on DPCM mode, only a limited selection of frequencies is available, and loop position isn't supported (only entire sample).
 - SegaPCM: your sample can't be longer than 65535, and the maximum frequency is 31.25KHz.
 - QSound: your sample can't be longer than 65535, and the loop length shall not be greater than 32767.
-- Neo Geo (ADPCM-A): no looping supported. your samples will play at ~18.5KHz.
-- Neo Geo (ADPCM-B): no loop position supported (only entire sample), and the maximum frequency is ~55KHz.
-- YM2608: the maximum frequency is ~55KHz.
+- Neo Geo (ADPCM-A): no looping supported. your samples will play at 18.518KHz.
+- Neo Geo (ADPCM-B): no loop position supported (only entire sample), and the maximum frequency is 55.555KHz.
+- YM2608: the maximum frequency is 55.555KHz.
 - MSM6258/MSM6295: no arbitrary frequency.
 - ZX Spectrum Beeper: your sample can't be longer than 2048, and it always plays at ~55KHz.
 - Seta/Allumer X1-010: frequency resolution is terrible in the lower end. your sample can't be longer than 131072.
diff --git a/doc/7-systems/opl.md b/doc/7-systems/opl.md
index b4a86e6db..80c002997 100644
--- a/doc/7-systems/opl.md
+++ b/doc/7-systems/opl.md
@@ -3,7 +3,7 @@
 a series of FM sound chips which were very popular in DOS land. it was so popular that even Yamaha made a logo for it!
 
 essentially a downgraded version of Yamaha's other FM chips, with only 2 operators per channel.
-however, it also had a drums mode, and later chips in the series added more waveforms (than just the typical sine) and even a 4-operator mode.
+however, it also had a [drums mode](opll.md), and later chips in the series added more waveforms (than just the typical sine) and even a 4-operator mode.
 
 the original OPL (Yamaha YM3526) was present as an expansion for the Commodore 64 and MSX computers (erm, a variant of it). it only had 9 two-operator channels and drums mode.
 
@@ -77,4 +77,4 @@ afterwards everyone moved to Windows and software mixed PCM streaming...
   - only in 4-op mode (OPL3).
 - `5Bxy`: set KSR of operator.
   - `x` is the operator (1-4; last 2 operators only in 4-op mode). a value of 0 means "all operators".
-  - `y` determines whether KSR is on.
\ No newline at end of file
+  - `y` determines whether KSR is on.
diff --git a/doc/7-systems/opll.md b/doc/7-systems/opll.md
index 8b16e8881..115e4bd70 100644
--- a/doc/7-systems/opll.md
+++ b/doc/7-systems/opll.md
@@ -12,7 +12,11 @@ OPLL also spawned a few derivative chips, the best known of these is:
 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
+- 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 mxier twice for 2x 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 syntheis mentioned already is: 5 square waves are gathered from 4x, 64x and 128x the pitch of channel 8 and 16x and 64x 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
@@ -60,4 +64,4 @@ the YM2413 is equipped with the following features:
 - `58xx`: set DR of operator 2.
 - `5Bxy`: set KSR of operator.
   - `x` is the operator (1-2). a value of 0 means "all operators".
-  - `y` determines whether KSR is on.
\ No newline at end of file
+  - `y` determines whether KSR is on.
diff --git a/doc/7-systems/ym2612.md b/doc/7-systems/ym2612.md
index 1eeb148e2..dda452665 100644
--- a/doc/7-systems/ym2612.md
+++ b/doc/7-systems/ym2612.md
@@ -1,6 +1,6 @@
 # Yamaha YM2612
 
-one of two chips that powered the Sega Genesis. It is a six-channel, four-operator FM synthesizer. Channel #6 can be turned into 8-bit PCM player.
+one of two chips that powered the Sega Genesis. It is a six-channel, four-operator FM synthesizer. Channel #6 can be turned into 8-bit PCM player, that via software mixing, thanks to Z80 sound CPU, can play more than one channel of straight-shot samples at once. As of Furnace 0.6pre5, Furnace offers DualPCM, which allows 2 channels of software-mixed 8-bit PCM samples at 13750 Hz.
 
 # effects