AULOS is a polyphonic physical-model wind instrument synthesizer built on a bidirectional digital waveguide: two traveling-wave rails run the length of the bore and reflect into one another at both the embouchure and the bell. REED and BORE reshape those two reflections directly, so they change the instrument's actual boundary conditions and harmonic series, not just a filter or a mix blend.
REED morphs the excitation and the embouchure reflection together. Near zero the bore is driven by an air-jet exciter with an open-end reflection — a flute's full harmonic series. Near maximum, the exciter becomes a pressure-driven beating reed and the embouchure reflection flips to a closed-end sign producing an odd-harmonic series sounding roughly an octave below the flute end, similar to a clarinet. The crossover in the middle interpolates between a jet and a reed — allowing to to access strange and characterful sounds.
BORE reshapes the bell reflection with a horn-cutoff model: below the cutoff frequency, energy reflects back into the tube and sustains the fundamental; above it, energy radiates out as sound. Raising BORE lowers that cutoff in two stages. Through roughly the first three-quarters of its range the tube widens like a clarinet body — fuller, richer harmonics, without going bright. In the top quarter it blooms into a flared brass/horn character, adding a waveform-steepening nonlinearity that converts low harmonics into upper partials. The panel display's tube silhouette mirrors this same two-stage curve, so the drawn bell shape blooms exactly where the tone turns brassy.
Register is determined by the ratio of the FINGER pitch to the PIPE fundamental. When the finger frequency is near twice the pipe frequency the bore shifts to the overblown octave; near four times, it shifts up a further octave. The transition smooths over roughly 200ms so the timbre morphs rather than snapping. Energy-overblow is a separate mechanism — very loud playing can momentarily push the mode upward independent of the finger position. Playing below the pipe fundamental is also supported, extending the bore rather than jamming — this is where the instrument's more unusual, whistling low-end character lives.
The graphical display shows two tube cross-sections, L on top and R below. Each tube depicts bore length, breath fill level, a standing-wave indicator, register, overblow outline, air lines streaming from the bell exit, and chiff line bursts on note attack. The tube's own silhouette widens and flares with BORE. The R tube dims to show the drone level reduction in drone mode.
Key controls:
- PIPE V/OCT input + PIPE TUNE knob (-1 to +4 oct): sets the resonant fundamental of the bore — the pitch the resonator naturally wants to sustain. Only this determines the resonant pitch; it does not have to track the played note.
- FINGER V/OCT input + FINGER TUNE knob (±1 oct): sets the fingering pitch, which determines bore length and register. In a standard melodic patch this tracks the played note. The ratio of FINGER to PIPE governs which register the bore locks to.
- GATE input: polyphonic up to 16 voices. Voice count follows the highest channel count across GATE, FINGER V/OCT, and PIPE V/OCT.
- BREATH knob + trim + CV: breath pressure, the physical driving force behind both exciters. At zero, neither the jet nor the reed produces any sound — silence, not a static tone. Past a light blowing threshold the note speaks and builds over its attack rather than switching on. Non-linearly scaled so low values are gentle; higher values push the instrument louder, into overblow, and harder-edged.
- REED slider + ATT + CV: excitation and embouchure morph, flute to reed (formerly EDGE). Near zero: air-jet exciter, open-end reflection, full harmonic series, breathy and hollow. Near maximum: beating-reed exciter, closed-end reflection, odd-harmonic series roughly an octave lower, buzzier and more stable across registers. The middle is a deliberately non-physical crossover zone with its own character.
- BORE slider + ATT + CV: bell reflection and horn shape, cylindrical to flared brass (formerly JET). Below ~0.75: the tube widens and fills out, restoring fuller harmonics without brightening. Above ~0.75: a brass-horn flare engages, brightening the tone and reshaping the harmonic balance rather than simply raising volume.
- DRIVE slider + ATT + CV: gain into the excitation-stage saturator. Shapes only the fresh excitation signal each sample, not the recirculating wave in the loop — the tube itself stays linear, so DRIVE adds harmonic richness at the source without threatening the loop's stability the way driving the whole resonator would.
- RES slider + ATT + CV (labeled Lip / Holes on panel): loop feedback gain, split across the two waveguide junctions. Higher values give a more resonant, sustaining tone. If the instrument goes unstable or squeals, reduce this.
- AIR slider + ATT + CV: breath noise amplitude. Injects noise into the excitation continuously. Displayed as the streaming air lines at the bell exit.
- CHIFF slider + ATT + CV: chiff transient duration and amplitude on each gate rise. At zero there is no attack burst; at maximum the chiff is long and loud. Displayed as the outer line bursts at the bell exit on each new note.
- AULOS slider + ATT + CV (±1 oct): R voice pipe pitch offset. Zero is unison. Positive raises the R pipe; negative lowers it.
- WOOD slider + ATT + CV: bore damping. Sweeps a low-pass filter inside the loop from fully open (bright) to deep cut (warm, dark), scaled with register so upper notes keep their harmonics instead of thinning out.
- VIBRATO input + ATT knob: when unpatched, the internal LFO drives pitch FM and breath wobble simultaneously. When patched, the external CV takes over pitch FM only; depth is set by the ATT knob in both cases.
- Manual Gate button: holds the gate high for all voices without a cable.
- Drone button + LED: toggles drone mode for the R voice. In drone mode the R voice gate is locked permanently on and plays at a slightly lower level than the envelope-gated L voice, fading in and out clicklessly when toggled. DRONE CV is a gate-triggered toggle.
- AUDIO IN input + AUDIO IN GAIN knob + trim + CV: injects external audio directly into the bore loop before the waveguide, exciting the resonance from outside.
- VOLUME knob + trim + CV: output gain, 0 to 3x.
- ENV output: polyphonic breath envelope.
- RMS output: polyphonic excitation dynamics follower.
- AUDIO L / AUDIO R: stereo outputs. The R voice only processes when AUDIO R is patched and is cleared on reconnect to avoid stale buffer playback.
- Blue VU (left cluster): breath envelope level per voice.
- Yellow VU (right cluster): excitation dynamics level per voice.
Context menu:
- Aulos R Voice Mode: Tracking (interval preserved) — the R finger shifts with the AULOS offset so both voices play the same interval in every register. Two Pipes (fixed registers) — R finger is independent and each pipe finds its own register from its own pipe frequency.
- Resonator: Waveguide Gain (raw loop input scaling for overall level balance), Decay (ring-off time after the gate falls).
- Envelope: Attack and Release (0..1 exponential time mappings), Attack Curve and Release Curve (negative = logarithmic, positive = exponential).
- Vibrato: Rate in Hz (3..12), Breath Coupling (how much the LFO modulates breath alongside pitch).
- Articulation: Legato toggle. When enabled, held-gate pitch changes glide rather than retriggering; the waveguide briefly dips feedback at each slur transition for the audible give between notes. Legato Glide Time sets the portamento duration in ms.
- Dynamics Envelope: Follow Time (integration time of the RMS follower driving the ENV and RMS outputs).
- Panic: immediately clears all waveguide and resonator energy.