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4.4 KiB
4.4 KiB
Yamaha YM2413/OPLL
the YM2413, otherwise known as OPLL, is a cost-reduced FM synthesis sound chip, based on the Yamaha YM3812 (OPL2).
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, 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 and1
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 of0
means "all operators".y
determines whether AM is on.
51xy
: set SL of operator.x
is the operator, either 1 or 2. a value of0
means "all operators".y
is the value.
52xy
: set RR of operator.x
is the operator, either 1 or 2. a value of0
means "all operators".y
is the value.
53xy
: set VIB of operator.x
is the operator, either 1 or 2. a value of0
means "all operators".y
determines whether VIB is on.
54xy
: set KSL of operator.x
is the operator, either 1 or 2. a value of0
means "all operators".y
is the value.
55xy
: set EGT of operator.x
is the operator, either 1 or 2. a value of0
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 of0
means "all operators".y
determines whether KSR is on.
info
this chip uses the FM (OPLL) instrument editor.
chip config
the following options are available in the Chip Manager window:
- Clock rate: sets the rate at which the chip will run.
- Patch set: changes the chip model, providing different built-in sounds.
the following options are visible in drums mode:
- 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.