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A series of FM sound chips which were very popular in DOS land. It was so popular that even Yamaha made a logo for it! Essentially a downgraded version of Yamaha’s other FM chips, with only 2 operators per channel. However, it also had a drums mode, and later chips in the series added more waveforms (than just the typical sine) and even a 4-operator mode. The OPL4 (Yamaha YMF278) retains the FM block from OPL3, but adds 24 sample channels on top! Samples are 44100 Hz, can be between 8, 12 or 16-bit, stereo (with 16 different levels) and can read PCM data from ROM or SRAM (up to 4 MB). Afterwards everyone moved to Windows and software mixed PCM streaming…

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Effects

  • 10xx: set AM depth. The following values are accepted:
    • 0: 1dB (shallow)
    • 1: 4.8dB (deep)
    • This effect applies to all channels.
  • 11xx: set feedback of channel.
  • 12xx: set operator 1 level.
  • 13xx: set operator 2 level.
  • 14xx: set operator 3 level.
    • Only in 4-op mode.
  • 15xx: set operator 4 level.
    • Only in 4-op mode.
  • 16xy: set multiplier of operator.
    • x is the operator (1-4; last 2 operators only in 4-op mode).
    • y is the new MULT value.
  • 17xx: set vibrato depth.
    • 0: normal
    • 1: double
    • This effect applies to all channels.
  • 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.
  • 1Cxx: set attack of operator 3.
    • Only in 4-op mode.
  • 1Dxx: set attack of operator 4.
    • Only in 4-op mode.
  • 2Axy: set waveform of operator.
    • x is the operator from 1 to 4; the last 2 operators only work in 4-op mode. A value of 0 means “all operators”.
    • y is the value.
  • 30xx: enable envelope hard reset.
    • This works by inserting a quick release and tiny delay before a new note.
  • 50xy: set AM of operator.
    • x is the operator from 1 to 4; the last 2 operators only work in 4-op mode. A value of 0 means “all operators”.
    • y determines whether AM is on.
  • 51xy: set SL of operator.
    • x is the operator from 1 to 4; the last 2 operators only work in 4-op mode. A value of 0 means “all operators”.
    • y is the value.
  • 52xy: set RR of operator.
    • x is the operator from 1 to 4; the last 2 operators only work in 4-op mode. A value of 0 means “all operators”.
    • y is the value.
  • 53xy: set VIB of operator.
    • x is the operator from 1 to 4; the last 2 operators only work in 4-op mode. A value of 0 means “all operators”.
    • y determines whether VIB is on.
  • 54xy: set KSL of operator.
    • x is the operator from 1 to 4; the last 2 operators only work in 4-op mode. A value of 0 means “all operators”.
    • y is the value.
  • 55xy: set SUS of operator.
    • x is the operator from 1 to 4; the last 2 operators only work in 4-op mode. A value of 0 means “all operators”.
    • y determines whether SUS is on.
  • 56xx: set DR of all operators.
  • 57xx: set DR of operator 1.
  • 58xx: set DR of operator 2.
  • 59xx: set DR of operator 3.
    • Only in 4-op mode.
  • 5Axx: set DR of operator 4.
    • Only in 4-op mode.
  • 5Bxy: set KSR of operator.
    • x is the operator from 1 to 4; the last 2 operators only work in 4-op mode. A value of 0 means “all operators”.
    • y determines whether KSR is on.

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Instrument Editor

This chip uses the FM (OPL) instrument editor for FM channels and the MultiPCM instrument editor for PCM channels. When two channels are joined for 4-op mode, the channel bar will show 4OP on a bracket tying them together. OPL4 maximum sample length is 65535.

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Chip Configuration

The following options are available in the Chip Manager window:
  • Clock rate: Sets the rate at which the chip will run.
  • RAM Size: Sets the RAM size for sample storage.

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