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furnace/doc/7-systems/opll.md

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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.