Doc touch-ups.

I think I know how that chunk of the TIA docs disappeared, but not how I missed it in double-checking the PR....

doc/1-intro/glossary.md

@@ -12,6 +12,8 @@
 
 **asset**: an instrument, wavetable or sample.
 
+**bit**: a single binary on-off value.
+
 **bitbang**: to achieve PCM sound by sending a rapid stream of volume commands to a non-PCM channel.
 
 **bitmask**: a set of bits which represent individual single-bit toggles or groups representing small numbers. these are explained fully in the [hexadecimal primer](hex.md).
@@ -72,7 +74,7 @@
 
 **LFO**: low frequency oscillator. a wave with a slow period (often below hearing range) used to alter other sounds.
 
-**LFSR**: linear-feedback shift register. an algorithm of generating pseudo-random noise that loops, also known as "periodic noise". depending on the location of the two "taps" used, different lengths of noise loops are generated.
+**LFSR**: linear-feedback shift register. a method to generate pseudo-random noise that loops, also known as "periodic noise". within a sequence of on-off bits, it does math to combine the bits at specified locations called "taps", then shifts the whole sequence and adds the resulting bit on the end, guaranteeing a different state for the next pass. depending on the locations of the taps, different lengths of noise loops are generated; for short loops, this will affect their tone.
 
 **macro**: a sequence of values automatically applied while a note plays.
 
@@ -130,6 +132,8 @@
 
 **supersaw**: a sound made up of multiple saw waves at slightly different frequencies to achieve a chorusing effect.
 
+**tap**: a specified bit location within an LFSR.
+
 **tick rate**: the number of times per second that the sound engine moves forward. all notes and effects are quantized to this rate.
 - this usually corresponds to the frame rate the system uses for video, approximately 60 for NTSC and 50 for PAL.