User’s Guide

A default bank of 2-operator algorithms is initially loaded. To get started with ADLplug, simply connect a MIDI keyboard and start playing.

The General MIDI standard applies: the MIDI channels are each associated with their melodic instrument, and channel 10 is associated with percussion.

Another bank can be selected from the included collections. This is done by clicking on , then opening the submenu via "Load from collection".

To understand how to edit programs, some understanding of FM synthesis, and specifically the OPL3, are required.

FM (frequency modulation) synthesis uses interconnected oscillators, also known as operators. The layout of these operators and connections are also known as algorithms. Each operator in an algorithm may act as either a modulator or a carrier.

The OPL3 has three classes of algorithms:

Pseudo-4-op is simply a pair of 2op voices played in unison. A peculiarity of this mode is that a tonal shift may be applied to the second voice with respect to the first.

First, select one of the three classes of algorithms.

Then, the FM and AM buttons are interpreted as follows:

The algorithm reference, opened by clicking on "?", displays the connection diagram corresponding to any combination of FM and AM.

The diagrams can be read as follows: blocks labelled from 1 to 4 are operators. Each operator in the bottom row is a carrier, and every other operator is a modulator. The diagrams also highlight the feedback loop on operator 1.

The amplitude of the signal fed back from operator 1 to itself can be controlled by the parameters "Feedback 1-2" and "Feedback 3-4".
Note: "Feedback 3-4" only applies to the second voice of 2x2op programs. In other configurations, it has no effect.

For tuning, "Note offset" is an offset in semitones applied to the note played. "Fine tune" is an additional offset in cents (hundredths of a semitone).
Note: "Note offset 3-4" and "Fine tune 3-4" apply only to the second voice of 2x2op programs. In other configurations, they have no effect.

"Percussion key" is the note that will be played if the instrument is used as percussion.

The program is played on the 18 general purpose channels of the OPL3.
For 2op algorithms, each of these channels can accommodate a single 2op voice.

For more complex instruments, it becomes more complicated.

The example above shows two OPL3 chips with 18 channels each. We have reserved 16 channels for 8 4op voices. Each voice has 2 channels, one colored pink and one colored blue. The remaining 20 channels in grey are available for 2op and 2x2op, allowing for polyphony of 20 or 10 voices respectively.

Maximum polyphony is controlled by the parameters "Chips" and "4 ops". The "4 ops" parameter is the maximum number of 4op voices, and must be no greater than 6 times the number of chips.

Clicking on automatically sets the "4 ops" parameter, based on the number of chips and the currently loaded bank. This value is a suggestion, and may not be optimal.

The synthesizer includes intelligent polyphony management that optimizes channel distribution. However, when channels are heavily occupied, and there are insufficient vacant channels to accommodate a new voice, an arpeggiation mechanism is triggered.

The arpeggiation allows a channel to be shared between 2 or more voices, rapidly switching the properties of the channel between the voices using it. This can create an illusion of polyphony, but also an audible distortion, which may sound uncomfortable in some situations.

Arpeggiation indicates insufficient polyphony. To prevent arpeggiation, the number of chips or 4op voices should be increased.

One of several YMF262 chip emulators may be selected. Emulators may be switched dynamically.

During the time required for switching emulators, the sound will be muted, and the MIDI stream will be ignored. This will not interfere with real-time operation.

The four operators, whether functioning as modulator or carrier, provide the same parameters.

The remaining parameters fall into two groups: Miscellaneous and Global.

A miscellaneous parameter applies to the currently selected program in the editor. On the other hand, a global parameter is a property of the bank, and applies to all programs in that bank.

"Velocity Offset" is a fixed modifier applied to the velocity of MIDI notes, and can be set in the range [-127, 127]. A positive offset increases velocity, and a negative value decreases it.

The "Deep tremolo" and "Deep vibrato" flags make those effects more pronounced, if they are active. The effect depths are fixed values determined by the design of the YMF262, and are as follows:

"Volume model" specifies a function for transforming the discrete parameters associated with volume into actual gain values. In most cases, the generic model is appropriate.

However, when loading banks from other software, the formula that reproduces the operation of that software should be selected. For example, if you load a bank from Doom, you should choose the DMX model. For Duke Nukem 3D, use Apogee.