MANTIS is a polyphonic digital synthesizer based on phase shaping and phase modulation: a stable low-end core, a clear tonal contour and moving, optionally inharmonic overtones. From focused basses and leads to slowly evolving textures.
Core
SubLevel of the sine sub oscillator one octave below the played note. It stays centred and is not affected by Weird or Fracture. Lowpass, the shared envelope and the space effects also affect the sub.
BodyLevel of the main synthesizer voice. Sub remains separately adjustable. With Body at 0, Edge, Motion, Weird and Fracture are no longer audible.
EdgeShapes the phase distortion and opens the internal tone filter: lower values are rounder and darker, higher values add harmonics and bite. Independent from the separate Lowpass control.
Modulation
MotionControls a regular movement in the tone through harmonic phase modulation and internal filter motion. The control changes depth, not speed.
WeirdAdds inharmonic phase modulation. Two short accents near the beginning of a note create distinctive transient colour, while a weaker modulation remains during the held note. MIDI modulation wheel controls this parameter.
FractureReshapes the upper spectrum with two continuous phase modulators. Higher values make their frequency relationships increasingly inharmonic; near the top of the range they move closer together again. This is not bit crushing or sample-rate reduction. The separate Sub remains unmodulated.
FM
FM Amt / RatioFM Amt controls the amount of frequency modulation applied to the Body oscillator. Ratio sets the modulator frequency ratio from 0.25 to 8. With FM Amt at 0, FM is effectively off. The Sub remains unmodulated.
HoldSets how much of the FM colour remains after a short fixed onset. At 0 the metallic component fades away; at 100% the selected FM amount is sustained. Rise and Settle are no longer separate FM parameters.
Filter
LowpassBase cutoff of the per-voice 2-pole lowpass filter. Range: 40 Hz to 18 kHz, or slightly lower at reduced sample rates. VEL MOD and SWEEP open the filter upward from this value and return to exactly this base setting.
Vel ModSets how strongly MIDI velocity opens the lowpass filter. At 0, velocity has no effect on the filter. At 100%, a hard strike can push the filter far into the open range.
SweepOn note-on, opens the lowpass from the selected base value and then closes it symmetrically back to the same value. The slider sets the time for each half of the sweep: off at the far left, then approximately 0.03 to 4 seconds to open, followed by the same time to close.
Master
RiseAttack time from 0.001 to 3 seconds. The voice reaches its envelope level over this period. The Rise value is captured when each note starts.
FallCombines decay, sustain and release in one control. At 0.01 s, a held note falls to essentially 0% sustain after the attack. Between 0.01 and 0.10 s, sustain rises continuously; at 0.10 s it reaches 100% and stays at full sustain above that point. When a note is released, the same Fall value also determines release time.
EnsembleA wide, soft stereo ensemble based on the principle of classic analogue chorus: two short, differently modulated delay lines create movement and width. At 0 the signal remains dry; higher values progressively blend in the ensemble effect.
EchoControls the level and feedback of the repeats together. Delay time is fixed at approximately 310 ms. At 0, no new signal is sent into the echo, while existing repeats are allowed to decay.
DistanceMoves the sound from close and dry to more distant by combining reverb level, pre-delay, short and long reverb tails and direct level. At 0, no new signal is sent into the reverb.
LevelOverall output level including echo and reverb. Randomize leaves Level unchanged. Presets recall their stored Level value.
Play and Control
Play / StopPlay holds the selected Root note. Stop releases it using the current Fall setting. There is no automatic note retriggering. Computer keyboard and MIDI can be played at the same time.
Root / HzSelects the root note used by Play, from C1 to B5. The adjacent display shows its frequency. Changing Root while Play is active releases the previous note and starts the new one. Root does not transpose MIDI or the computer keyboard.
MIDISelect an available MIDI input from the menu. Opening or selecting the MIDI menu activates the audio engine, so the Play button is not required. Note-on starts a note and note-off releases it. Velocity controls note level and can also open the filter through VEL MOD. CC1 (modulation wheel) controls Weird. Sustain pedal, pitch bend and aftertouch are not implemented.
Computer KeyboardA W S E D F T G Y H U J K play chromatically from C to the next C. Z lowers the octave and X raises it. At startup, A plays C3. The page must have keyboard focus to play; text input fields are excluded. Held computer-keyboard notes are released when the browser window loses focus.
Audio StartThe engine is prepared when the page loads. A click, key press or MIDI-device selection activates audio automatically. Some browsers do not treat a raw MIDI note-on as a valid audio-unlock gesture, so one interaction with the page or MIDI menu may still be required. The Play button itself is not required for initialization.
Preset 1–9Presets recall complete MANTIS settings. The selected preset button is shown inverted. Changing any control, using Randomize or moving the modulation wheel clears the active preset indication.
RandomizeCreates a new set of parameter values within the available ranges. Level is left unchanged. Randomize also clears the active preset indication.
WaveformShows the output waveform including effects. It is a time-domain display, not a frequency spectrum.
LissajousShows the relationship between the left and right output channels as a stereo phase figure. A narrow diagonal shape indicates a more mono-compatible signal; wider shapes reflect increasing stereo difference and movement.
Scope ModeSwitches both displays between the clean Classic view and the green phosphor-style oscilloscope view. The display mode does not affect the sound.
Dark / BrightSwitches between dark and bright interface modes. The selection is stored locally when the browser allows it.
Info / CloseThe i button opens this manual. Close or Escape closes it.
ToneveldThe Toneveld name links back to the Toneveld website.