Limits of Guitar Study #1: Harmonic Sequences

harmonics.lua

-- harmonics

engine.name = "Sines"

function init()
  root_note = 30
  base_freq = midi_to_hz(root_note)

  freqs = {}
  amps = {}
  levels = {}
  num_harmonics = 12
  release_time = 5
  generate_new_random_harmonics()

  is_playing = false
  note_playing = false
  pulse_rate = 0.75
  pulse = metro.alloc(play_note, pulse_rate, -1)

  is_changing = false
  change_rate = 2.0
  harmonic_changes = metro.alloc(generate_new_random_harmonics, change_rate, -1)
end

function redraw()
  screen.clear()
  draw_harmonics()
  draw_play_status()
  draw_change_status()
  screen.update()
end

function draw_harmonics()
  screen.move(10, 10)
  screen.level(10)
  screen.text("Harmonics")
  for i = 1, num_harmonics do
    screen.move(10 * i, 20)
    screen.level(levels[i])
    screen.text("#")
  end
end

function draw_play_status()
  play_level = 2
  if is_playing then
    play_level = 12
  end
  screen.move(10, 60)
  screen.level(play_level)
  screen.text("P")

  screen.move(20, 60)
  pr = math.ceil(util.linlin(0.25, 2, 1, 10, pulse_rate))
  screen.text(pr)
end

function draw_change_status()
  change_level = 2
  if is_changing then
    change_level = 12
  end
  screen.move(40, 60)
  screen.level(change_level)
  screen.text("C")

  screen.move(50, 60)
  cr = math.ceil(util.linlin(0.25, 5, 1, 10, change_rate))
  screen.text(cr)
end

function play_note()
  if note_playing then
    silence_harmonics()
    note_playing = false
  else
    play_harmonics()
    note_playing = true
  end
end

function key(n, z)
  if n == 2 and z == 1 then
    if (is_playing == false) then
      pulse:start()
      is_playing = true
    else
      is_playing = false
      pulse:stop()
      silence_harmonics()
    end
  end

  if n == 3 and z == 1 then
    if (is_changing) then
      harmonic_changes:stop()
      is_changing = false
    else
      harmonic_changes:start()
      is_changing = true
    end
  end

  redraw()
end

function enc(n, d)
  if (n == 2) then
    pr = util.linlin(0, 2, 1, 10, pulse_rate)
    pr = util.clamp(pr + d, 1, 10)
    pulse_rate = util.linlin(1, 10, 0.25, 2, pr)
    pulse.time = pulse_rate
  end
  if (n == 3) then
    cr = util.linlin(0, 5, 1, 10, change_rate)
    cr = util.clamp(cr + d, 1, 10)
    change_rate = util.linlin(1, 10, 0.25, 5, cr)
    harmonic_changes.time = change_rate
  end
  redraw()
end

function play_harmonics()
  local f_debug = "Freqs: "
  for i = 1, num_harmonics do
    engine.amp_atk(i, 1)
    engine.amp(i, amps[i])
    engine.hz(i, freqs[i])
    f_debug = f_debug .. freqs[i]
  end
  print(f_debug)
end

function silence_harmonics()
  for i = 1, num_harmonics do
    engine.amp(i, 0)
  end
end

function generate_new_random_harmonics()
  for i = 1, num_harmonics do
    freqs[i] = base_freq * i
    local r = math.random()
    amps[i] = util.linexp(0, 1, 0.2, 0.8, r)

    -- levels is for visual representation of harmonic strength
    levels[i] = math.floor(util.linlin(0, 1, 1, 14, r))
    engine.amp_rel(i, release_time)
  end
  redraw()
end

function midi_to_hz(note)
  return (440 / 32) * (2 ^ ((note - 9) / 12))
end