Several more sys/inst doc updates.

doc/4-instrument/wonderswan.md

@@ -8,11 +8,11 @@ for sample settings, see [the Sample instrument editor](sample.md).
 
 the only differences are the lack of an "Use wavetable" option, and the presence of a "Use sample" one.
 
-only on channel 2!
+only available on channel 2!
 
 ## Wavetable
 
-this allows you to enable and configure the Furnace wavetable synthesizer. see [this page](wavesynth.md) for more information.
+this allows you to enable and configure the Furnace wavetable synthesizer. see the [wavesynth documentation](wavesynth.md) for more information.
 
 ## Macros
 

doc/7-systems/tia.md

@@ -35,13 +35,13 @@ a song can be exported to assembly code for use with the TIunA software driver f
 
 the following options are available in the Chip Manager window:
 
-- **Software pitch driver**: use TIunA, a software pitch driver similar to TIATune. it increases pitch precision by rapidly switching between two pitches.
+- **Software pitch driver**: use TIunA, a software pitch driver similar to TIATune. it increases pitch precision by rapidly switching between two pitches. pitches are still limited to their original range; see pitch tables below.
 - **Old pitch table**: use an older method to calculate pitch. only for compatibility.
 - **Mixing mode**: changes mixing mode.
   - **Mono**: normal output.
   - **Mono (no distortion)**: process each channel separately to eliminate distortion.
   - **Stereo**: output two channels on left and right.
-- **PAL**: run slower blah blah blah
+- **PAL**: runs at a slightly different clock rate, affecting pitch.
 
 ## info
 

doc/7-systems/wonderswan.md

@@ -4,9 +4,11 @@ a handheld console released only in Japan by Bandai, designed by the same people
 for this reason it has lots of similar elements from those two systems in the sound department.
 
 it has 4 wavetable channels. some of them have additional capabilities:
-- the second channel could play samples
-- the third one has hardware sweep
-- the fourth one also does noise
+- the second channel could play samples.
+- the third one has hardware sweep.
+- the fourth one also does noise.
+
+unfortunately, the system mixes and outputs sound at only 24kHz, leading to noticeable aliasing noise...
 
 ## effects
 
@@ -15,8 +17,8 @@ it has 4 wavetable channels. some of them have additional capabilities:
   - 0: disable.
   - 1-8: enable and set length.
 - `12xx`: **setup sweep period.** channel 3 only.
-  - 0: disable.
-  - 1-32: enable and set period.
+  - `00`: disable.
+  - `01`-`20`: enable and set period for 1 to 32.
 - `13xx`: **setup sweep amount.** channel 3 only.
   - `00` to `7F` for 0 to 127.
   - `80` to `FF` for -128 to -1.

doc/7-systems/ym2203.md

@@ -1,13 +1,8 @@
 # Yamaha YM2203 (OPN)
 
-a cost-reduced version of the YM2151 (OPM).
-it only has 3 FM channels instead of 8 and removes stereo, the LFO and DT2 (coarse detune).
+a cost-reduced version of the YM2151 (OPM). it only has 3 FM channels instead of 8 and removes stereo, the LFO and DT2 (coarse detune). however, it does contain an AY/SSG part which provides 3 channels of square wave with noise and envelope.
 
-however it does contain an AY/SSG part which provides 3 channels of square wave with noise and envelope.
-
-this chip was used in the NEC PC-88/PC-98 series of computers, the Fujitsu FM-7AV and in some arcade boards.
-
-several variants of this chip were released as well, with more features.
+this chip was used in the NEC PC-88/PC-98 series of computers, the Fujitsu FM-7AV and in some arcade boards. it went on to become the basis for several other OPN chips.
 
 ## effects
 

doc/7-systems/ym2612.md

@@ -1,4 +1,4 @@
-# Yamaha YM2612
+# Yamaha YM2612 (OPN2)
 
 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. 
 Furnace also offers DualPCM, a Z80 driver that splits channel 6 into two individual PCM channels with variable pitch. using the console's Z80 processor, these are mixed together in software and streamed to channel 6 in PCM mode with a mix rate of 13750 Hz. VGM export requires the "direct stream mode" option to be enabled, and resulting files will be very large.