75 lines
4.1 KiB
Markdown
75 lines
4.1 KiB
Markdown
# Yamaha YM2413/OPLL
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the YM2413, otherwise known as OPLL, is a cost-reduced FM synthesis sound chip, based on the Yamaha YM3812 (OPL2).
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OPLL also spawned a few derivative chips, the best known of these is:
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- 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...
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- Yamaha YM2423, same chip as YM2413, just a different patch set...
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- Yamaha YMF281, ditto.....
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## technical specifications
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the YM2413 is equipped with the following features:
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- 9 channels of 2 operator FM synthesis
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- 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.
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- 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.
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- 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.
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- **1 user-definable patch (this patch can be changed throughout the course of the song)**
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- **15 pre-defined patches which can all be used at the same time**
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- support for ADSR on both the modulator and the carrier
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- sine and half-sine based FM synthesis
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- 9 octave note control
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- 4096 different frequencies for channels
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- 16 unique volume levels (NOTE: volume 0 is NOT silent.)
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- modulator and carrier key scaling
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- built-in hardware vibrato support
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## effects
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- `11xx`: **set feedback of channel.**
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- `12xx`: **set operator 1 level.**
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- `13xx`: **set operator 2 level.**
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- `16xy`: **set multiplier of operator.**
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- `x` is the operator, either 1 or 2.
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- `y` is the new MULT value..
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- `18xx`: **toggle drums mode.**
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- `0` disables it and `1` enables it.
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- only in drums mode.
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- `19xx`: **set attack of all operators.**
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- `1Axx`: **set attack of operator 1.**
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- `1Bxx`: **set attack of operator 2.**
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- `50xy`: **set AM of operator.**
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- `x` is the operator, either 1 or 2. a value of `0` means "all operators".
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- `y` determines whether AM is on.
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- `51xy`: **set SL of operator.**
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- `x` is the operator, either 1 or 2. a value of `0` means "all operators".
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- `y` is the value.
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- `52xy`: **set RR of operator.**
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- `x` is the operator, either 1 or 2. a value of `0` means "all operators".
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- `y` is the value.
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- `53xy`: **set VIB of operator.**
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- `x` is the operator, either 1 or 2. a value of `0` means "all operators".
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- `y` determines whether VIB is on.
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- `54xy`: **set KSL of operator.**
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- `x` is the operator, either 1 or 2. a value of `0` means "all operators".
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- `y` is the value.
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- `55xy`: **set EGT of operator.**
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- `x` is the operator, either 1 or 2. a value of `0` means "all operators".
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- `y` determines whether EGT is on.
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- `56xx`: **set DR of all operators.**
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- `57xx`: **set DR of operator 1.**
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- `58xx`: **set DR of operator 2.**
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- `5Bxy`: **set KSR of operator.**
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- `x` is the operator, either 1 or 2. a value of `0` means "all operators".
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- `y` determines whether KSR is on.
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## info
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this chip uses the [FM (OPLL)](../4-instrument/fm-opll.md) instrument editor.
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## chip options
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- **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.
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- **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.
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