This is an example of how to apply a custom vibrato to a single voice.
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--! @example vibrato.lua
--! This is an example of how to apply a custom vibrato to a single voice.
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Freq = Knob("Freq", 4.0, 0, 10) -- 4 Hz
Depth = Knob("Depth", 0.5, 0, 1)

local step = 5 -- ms

function onNote(e)  
  local id = postEvent(e) -- duration is omitted

  local phase = 0
  while isNoteHeld() do
    local depth = Depth.value
    local freq = Freq.value  
        
    local modulation = depth * math.sin(2 * math.pi * phase)
    changeTune(id, modulation)
    
    wait(step)
    
    phase = phase + (step/1000.0) * freq
  end
end