Yamaha YM2413 (OPLL)

• 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 and no drums mode…
• Yamaha YM2423, same chip as YM2413, just a different patch set…
• Yamaha YMF281, also changes the patch set…

​

Technical Specifications

• 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. 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
• 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

• 10xx: change patch.
• 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 new MULT value.
• 18xx: toggle drums mode.
  • 0 disables it and 1 enables it.
  • Only in drums mode.
• 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.

​

Instrument Editor

​

Chip Configuration

• Clock rate: Sets the rate at which the chip will run.
• Patch set: Changes the chip model, providing different built-in sounds.

• Ignore top/hi-hat frequency changes: In drums mode, makes the top/hi-hat channels not write frequency since they share it with snare and tom.
• Apply fixed frequency to all drums at once: Sets the frequency of all drums to that of a fixed frequency OPLL drums instrument when one note with it is reached.