Update opll.md

formatting

doc/7-systems/opll.md

@@ -15,8 +15,8 @@ the YM2413 is equipped with the following features:
 - 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. channel 9 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
+- **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
 - sine and half-sine based FM synthesis
 - 9 octave note control