more updates

doc/4-instrument/README.md

@@ -74,6 +74,7 @@ the following instrument types are available:
 - [TED](ted.md) - for use with Commodore Plus/4 and Commodore 16's TED chip.
 - [C140](c140.md) - for use with C140 sample chip.
 - [C219](c219.md) - for use with C219 sample chip.
+- [PowerNoise](powernoise.md) - for use with PowerNoise chip.
 
 ## macros
 
@@ -91,9 +92,6 @@ each macro has the following parameters:
   - **Step Length (ticks)**: determines the number of ticks between macro steps. default is 1.
   - **Delay**: delays the macro until this many ticks have elapsed. default is 0.
   - the button is highlighted if either of these parameters is set to non-default values.
-- release mode: determines how macro release (`===` or `REL` in the pattern) is handled:
-  - **Active**: jumps to release position on release.
-  - **Passive**: does not jump to release position. this will result in delay if release position has not been reached yet.
 
 ## macro types
 
@@ -167,6 +165,10 @@ the sequence can be edited in the text input field at the very bottom. the follo
 
 in bitmask-style macros, the values are added up in binary and converted to decimal.
 
+the release mode parameter determines how macro release (`===` or `REL` in the pattern) is handled:
+- **Active**: jumps to release position on release.
+- **Passive**: does not jump to release position. this will result in delay if release position has not been reached yet.
+
 ### ADSR
 
 ![ADSR macro editor](macro-ADSR.png)

doc/4-instrument/lynx.md

@@ -24,6 +24,20 @@ note that using samples on Lynx is CPU expensive!
 
 Atari Lynx generates sound using a 12-bit linear feedback shift register with configurable tap. nine separate bits can be enabled to be the source of feedback: 0, 1, 2, 3, 4, 5, 7, 10 and 11. to generate _any_ sound at least one bit _must_ be enabled.
 
+### LFSR-based synthesis
+
+a linear-feedback shift register is one method used for random number generation.
+it works by shifting a sequence of binary numbers (bits), taking the last bit into the output. then some of the bits are combined with others, doing a XOR (exclusive or) operation and then being pushed back.
+
+think of it as a conveyor carrying glass bottles. each bottle may be empty or carrying water.
+the bottle at the end is taken. if there's water, then the output is 1. if it's empty, the output is 0.
+depending on the LFSR configuration, many bottles at specific positions ("taps") are looked at. these are combined from left to right, two by two:
+- if two bottles are identical, an empty bottle is pushed.
+- if one bottle has water but the other is empty, a water bottle is pushed.
+the process is repeated indefinitely.
+
+unlike PowerNoise, Lynx's taps are in fixed positions, but it has many of them.
+
 ### square wave
 
 the LFSR is shifted at the rate define by sound pitch and generates square wave by setting channel output value to +volume or -volume, depending on the bit shifted in.

doc/4-instrument/powernoise.md

@@ -15,7 +15,7 @@ depending on the LFSR configuration:
 - a bottle is pushed into the conveyor. it is either empty or filled with water depending on the bottle at a specific position in the conveyor (this is called a "tap"), or
 - two bottles at specific positions ("taps") are looked at and combined as follows:
   - if the bottles are identical, an empty bottle is pushed.
-  - if one bottle has water but the other is empty, a watee bottle is pushed.
+  - if one bottle has water but the other is empty, a water bottle is pushed.
 the process is repeated indefinitely.
 
 PowerNoise uses either one or two taps for the LFSR, configurable via the Control macro.

doc/7-systems/README.md

@@ -90,6 +90,7 @@ this is the full list of chips that Furnace supports.
 - [PET](pet.md)
 - [Pokémon Mini](pokemini.md)
 - [POKEY](pokey.md)
+- [PowerNoise](powernoise.md)
 - [PV-1000](pv1000.md)
 - [QSound](qsound.md)
 - [RF5C68/RF5C164](ricoh.md)