OPAL instrument

OPAL is a two-operator FM synthesizer inspired by OPL-era PC sound hardware. Each instrument is monophonic. Any of the 64 instrument slots can hold an OPAL preset, subject to available memory; there is no fixed three-preset limit.

General settings lead into two aligned operator columns.

Instrument settings

Field	Values	Default	Behaviour
ALGORITHM	1*2, 1+2	1*2	Serial FM (operator 1 modulates 2) or parallel/additive output.
DEEP TREM/VIB	Two bits	00	Global deep-tremolo and deep-vibrato flags.
FEEDBACK	0–7	0	Feedback amount for operator 1.

For DEEP TREM/VIB, hold Enter, choose the tremolo or vibrato bit with Left / Right, and toggle it with Up / Down.

Operator settings

The blue Operator Settings divider shares a row with OP 1 and OP 2. The active operator header highlights only while an operator field is focused. The two operators appear side by side below it. Up / Down moves by row. Left / Right without Enter switches operator columns; hold Enter while changing the selected operator's value.

Field	Values	OP1 default	OP2 default	Behaviour
LEVEL	00–3F	17	00	Output attenuation: 00 is loudest and 3F is quietest.
MULTIPLIER	0–F	1	1	Operator frequency multiplier.
A/D/S/R	Four hex digits	F1C8	F1D8	Attack, decay, sustain, and release.
SHAPE	Eight choices	SINE	SINE	SINE, HALF, ABS, PULS, EVEN, AB-E, SQR, or DSQR.
TR/VB/SU/KSR	Four bits	0000	0010	Tremolo, vibrato, sustained envelope, and key-rate scaling flags.
KEYSCALE	0, 1.5, 3, 6	1.5	0	Selects the displayed high-note attenuation curve.

A/D/S/R and TR/VB/SU/KSR are component fields: hold Enter, select a digit or bit with Left / Right, then edit it with Up / Down.

Voice behaviour

One OPAL instrument owns one synth channel. If the same instrument number is triggered by several tracker tracks, a later note replaces the earlier note. Allocate another OPAL slot for another simultaneous voice.