5 · Effects & the Global EFX Bus

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GDVP has two distinct places effects can live, and one of them is largely dormant on the current build. This chapter explains both honestly so you know what actually processes sound.

5.1 Two domains: per-voice vs. master

Per-voice (local domain). Nodes inside a patch run once per sounding voice. Filtering, amplitude, panning and (designed) per-voice GFX happen here. Ten notes = ten independent copies.
Master domain (Global EFX bus). A single, monophonic chain that processes the summed output of all voices. This is the right place for reverb and delay — you want one shared room, not one per note. The VAM reserves a dedicated EFX node pool for it (efx_pool[8], efx_active_plan, with its own SPSC staging), flagged GDVP_NODE_FLAG_MASTER_DOMAIN. Source: gdvp_vam_elastic_t in gdvp_voice_manager.h.

The design intent: spatial acoustics (reverb/delay/diffusion) on the master bus; tone-shaping (filter, saturation) per voice.

5.2 The GFX family (active effects)

The GFX nodes are the in-graph effects engine — delay, FDN reverb, all-pass phaser/diffuser, nonlinear gain (sat/fold/µ-law/ring), envelope-follower dynamics, and a universal parameter modulator. They're built on a small set of reusable primitives ("G×T decomposition") so many named effects share a few DSP cells.

✅ Status: the GFX family is fully wired

Every GFX slot in gdvp_node_processors[] and gdvp_node_updaters[] is now populated. The voice executor runs them on the Global EFX Bus (master domain, post-mix, monophonic) so spatial acoustics and global modulation are rendered as designed. The master_bus node type remains reserved/inactive; master fold-down and Global EFX scheduling are handled by the gdvp_dsp_iron_ceiling pipeline.

Full per-node design detail is on the GFX page.

5.3 What actually shapes sound today

Working, audible processing on the current build:

Effect	Where	How
Saturation / soft-clip	VCA	tanh LUT on the amp output (`saturation_enabled`)
Filter drive	Filter	pre-gain into the filter saturation stage
Filter sweeps / wah	LFO or Envelope → filter port 1	modulate cutoff
Vibrato / PWM	LFO → oscillator	modulate pitch / pulse width
Tremolo / auto-pan	LFO → VCA / Panner	modulate gain / pan
Noise & texture	Exciter	colored noise, dust, S&H
Strum / echo (voices)	DELAY voice mode	staggered-onset voices — not a delay line, but it works
Stereo width (per voice)	Panner	constant-power placement

So while the dedicated reverb/delay/phaser nodes are dormant, you can still build expressive, moving, saturated, stereo patches today using modulation routing and the VCA/filter nonlinearities.

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