TRIOSOUNDstacks three oscillatorslight / dark

TRIO

TRIO is three oscillators with ring modulation and hard sync (one oscillator restarting another every cycle) into a low-pass, band-pass, high-pass or notch filter, after the sound chips in early 8-bit home computers.

stacks three oscillators

Half

SOUND

Reach it

a custom build, FELUCCA_TRIO=1 (else on ANALOG)

ALGORITHM

WAVE

Engine

TRIO

Factory sounds

5

Playing it

MAIN holds the filter's CUT and RES, PW (the pulse width, for the waves that use a pulse), and INT2, the interval of the second oscillator in semitones. Set INT2 to 7 or 12 for fifths or octaves stacked in one note.

WAVE, on the OSC page, is the big choice: each setting is a whole set of three waves, their levels and how they interact.

TRIO is on the sidelines: SQRL-1's build leaves it out. A custom build with FELUCCA_TRIO=1 brings it back, picked on the PAIR page (hold HOME, tap GLO, KNOB 1). Without it, a TRIO sound in a project or a saved sound plays on ANALOG.

MAIN

Pages

OSC

WAVE picks the set. Some stack three of one wave (SAW3, PLS3, TRI3); some combine two waves the way those chips did, with a bitwise AND (S&T, P&S); the SYNC settings restart oscillator 2 at every cycle of oscillator 1; the RING settings flip oscillator 1's sign with oscillator 3 for a metallic ring. INT2 and INT3 tune oscillators 2 and 3 against the note, and DTN spreads them apart in cents (2 up, 3 down).

Knob	Label	Range	Starts at
1	WAVE	16 values SAW3 PLS3 PPT SST TRI3 S&T P&S P+N NOIS SYNC SYNCP SYNC3 RING RING3 R+S R+SP	SAW3
2	INT2	-24st .. +24st	0st
3	INT3	-24st .. +24st	-12st
4	DTN	0ct .. 50ct	9ct

TONE

MODE picks low-pass, band-pass, high-pass or notch. The resonance stops short of self-oscillation and gets gritty instead of ringing when pushed, and the cutoff drifts slowly, like an old chip's.

Knob	Label	Range	Starts at
1	MODE	LP BP HP NOT	LP
2	CUT	30Hz .. 16.0kHz	643Hz
3	RES	0% .. 100%	35%
4	PW	0% .. 100%	50%

Where it comes from

firmware/src/eng_trio.c, Felucca's own design (GPL-3.0), by Leo Kuroshita, Hügelton Instruments.