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OpulenZ is an emulation of the Yamaha YM3812, a.k.a OPL2, FM synth chip which was used in sound cards around 1990 - the Adlib and Sound Blasters. It generates sound through frequency modulation or adding 2 oscillators.



The two oscillators are called operators. In FM mode (bottom left), operator 1 modulates operator 2. Otherwise both operators are routed to the output.


For each operator, the controls are:

  • ATT, DEC, SUS, REL - an ADSR envelope.
  • KSR - keyboard scaling rate. When KSR is on, envelopes get faster when the pitch rises.
  • PERC - percussive envelope, makes the envelope go straight to release ignoring held keys.
  • TREM - applies tremolo (slight amplitude modulation) to the operator.
  • VIB - applies vibrato (slight pitch modulation) to the operator.
  • FEEDBACK (only for operator 1) - feeds a portion of the operator's output back into it.
  • LVL - the output level of the operator.
  • SCALE - determines the scaling applied to the output level when the pitch rises.
  • MUL - the frequency multiplier for the operator. 1 stands for the standard pitch played on the keyboard, 0 is one octave below.
  • WAVEFORM - selection from 4 waveforms: sine, half sine, absolute sine and quarter sine. NB: a DC removal plugin might be a good idea when routing waveforms other than sine to the output.

Global controls

  • FM - when this is on, frequency modulation is used. Otherwise the operators are mixed together.
  • DEPTH, TREM and VIBR - these select deeper tremolo and vibrato. Applies to both operators.

Useful resources

Getting started with FM: http://www.gorenfeld.net/lou/fmguide.html

Programming the AdLib/Sound Blaster FM Music Chips: http://www.shipbrook.net/jeff/sb.html (some of the controls are presented inverted in LMMS, to fit better with other synths)


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