furnace/doc/7-systems/opll.md

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
• 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 (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 (1-2). a value of 0 means "all operators".
  • y determines whether AM is on.
• 51xy set SL of operator.
  • x is the operator (1-2). a value of 0 means "all operators".
  • y is the value.
• 52xy set RR of operator.
  • x is the operator (1-2). a value of 0 means "all operators".
  • y is the value.
• 53xy: set VIB of operator.
  • x is the operator (1-2). a value of 0 means "all operators".
  • y determines whether VIB is on.
• 54xy set KSL of operator.
  • x is the operator (1-2). a value of 0 means "all operators".
  • y is the value.
• 55xy set EGT of operator.
  • x is the operator (1-2). 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 (1-2). a value of 0 means "all operators".
  • y determines whether KSR is on.