Purpose

Halo is a bright-register tonal instrument built on physical models and FM synthesis. Six modes cover plucked strings, struck bars, electric piano tines, bells, bowed glass, and vocal pads. It is the upper-register companion to Deep Beast (low end) and Synth (subtractive mid-range).

TouchDesigner Use

Wire note_voices_f32_v1 into the voices input from MIDI Note, a chord voicer, an arpeggiator, or any note-voice source. Choose a mode, shape the timbre with the performance controls, and wire the stereo audio output to Device Out, an effect chain, or a mixer.

Inputs And Outputs

• Input 0: voices — note_voices_f32_v1 (required). Gate, pitch, velocity, and aftertouch per voice.
• Output 0: out — stereo audio (PCM f32).

Main Controls

• Mode — Voice character: pluck (Karplus-Strong delay-line string/harp), mallet (modal resonator bank, struck bar/glass/vibe), keys (2-op FM tine, Rhodes/electric piano), bell (inharmonic 2-op FM bell), glass (bowed, sustained-excited resonator pad), choir (formant/vowel filtered pad).
• Gain — Output level.
• Tone — Overall brightness (post-synthesis LP filter cutoff).
• Damp — High-frequency damping in the pluck delay line. Lower values sustain brighter; higher values darken faster.
• Decay — Ring/sustain length. In FM modes (keys, bell), controls the percussive brightness decay.
• Position — Excitation position. In pluck mode, moves the pluck point from bridge (bright) to center (mellow). In mallet/glass modes, shapes the excitation burst character.
• Structure — Mode-specific timbre control. In mallet mode, morphs partial ratios from harmonic to bar-like inharmonic. In FM modes, sets the modulator frequency ratio. In choir mode, morphs through ah/ee/oo vowels.
• Resonance — Resonator Q / feedback intensity.
• Drive — Post-synthesis saturation.
• Shimmer — Octave-up resonant halo. Adds a high-Q partial one octave above the fundamental for sparkle and shimmer.
• Width — Stereo spread of voice panning.
• Spread — Per-voice pan offset spread.
• Velsens — Velocity sensitivity.
• Release — Amplitude envelope release time (5 ms to 2 s).
• Limiter — Output safety limiter.

Notes

• Up to 8 polyphonic voices.
• Pluck mode uses a Karplus-Strong delay line with linear interpolation and a position-dependent comb tap for tonal variation.
• Mallet mode uses 4 bandpass resonators with morphable partial ratios (harmonic 1:2:3:4 to bar-like 1:2.76:5.40:8.93).
• FM modes (keys, bell) use a 2-operator FM chain where the modulation index decays with the percussive envelope for bright attack and warm sustain.
• Glass mode uses the same modal bank as mallet but with continuous noise excitation instead of a strike burst, producing a sustained bowed/air sound.

Parameters

This operator does not expose user parameters in the extracted schema.

Catalog metadata

Roles

• transform
• instrument
• generator
• resonator

Tags

• physical-model
• karplus-strong
• modal
• fm
• pluck
• mallet
• bell
• glass
• formant
• note_voices

Search groups

• midi
• control
• audio
• music
• instrument
• synth