etc
/
furnace
mirror of https://github.com/tildearrow/furnace.git
0
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity
furnace/doc/7-systems/opll.md

3.8 KiB
Raw Blame History

Yamaha YM2413/OPLL

the YM2413, otherwise known as OPLL, is a cost-reduced FM synthesis sound chip, based on the Yamaha YM3812 (OPL2). thought OPL was downgraded enough? :p

OPLL also spawned a few derivative chips, the best known of these is:

  • the famous Konami VRC7. used in the Japan-only video game Lagrange Point, it was another cost reduction on top of the OPLL! this time just 6 channels...
  • Yamaha YM2423, same chip as YM2413, just a different patch set
  • Yamaha YMF281, ditto

technical specifications

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, 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. 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 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

  • support for ADSR on both the modulator and the carrier

  • sine and half-sine based FM synthesis

  • 9 octave note control

  • 4096 different frequencies for channels

  • 16 unique volume levels (NOTE: volume 0 is NOT silent.)

  • modulator and carrier key scaling

  • built-in hardware vibrato support

effects

  • 11xx: set feedback of channel.
  • 12xx: set operator 1 level.
  • 13xx: set operator 2 level.
  • 16xy: set multiplier of operator.
    • x is the operator, either 1 or 2.
    • y is the multiplier.
  • 18xx: toggle drums mode.
    • 0 disables it and 1 enables it.
    • only in drums chip.
  • 19xx: set attack of all operators.
  • 1Axx: set attack of operator 1.
  • 1Bxx: set attack of operator 2.
  • 50xy: set AM of operator.
    • x is the operator, either 1 or 2. a value of 0 means "all operators".
    • y determines whether AM is on.
  • 51xy: set SL of operator.
    • x is the operator, either 1 or 2. a value of 0 means "all operators".
    • y is the value.
  • 52xy: set RR of operator.
    • x is the operator, either 1 or 2. a value of 0 means "all operators".
    • y is the value.
  • 53xy: set VIB of operator.
    • x is the operator, either 1 or 2. a value of 0 means "all operators".
    • y determines whether VIB is on.
  • 54xy: set KSL of operator.
    • x is the operator, either 1 or 2. a value of 0 means "all operators".
    • y is the value.
  • 55xy: set EGT of operator.
    • x is the operator, either 1 or 2. a value of 0 means "all operators".
    • y determines whether EGT is on.
  • 56xx: set DR of all operators.
  • 57xx: set DR of operator 1.
  • 58xx: set DR of operator 2.
  • 5Bxy: set KSR of operator.
    • x is the operator, either 1 or 2. a value of 0 means "all operators".
    • y determines whether KSR is on.

info

this chip uses the FM (OPLL) instrument editor.