f0 = 440
fa = math.pow(2, 1 / 12)

function tone2freq(tone)
  return f0 * math.pow(fa, tone)
end

square = audio.new()
function _init()
  len = 8
  audio.samplelength(square, len)
  while len > 0 do
    len = len - 1
    val = 15
    if len < 4 then
      val = -16
    end
    audio.samplevalue(square, len, val)
  end
  audio.sampleloop(square, 0, 8)
  start, endd = audio.sampleloop(square)
  for chan = 0, 3 do
    audio.play(chan, square)
  end
  sys.stepinterval(240)
end

vol = 63
pos = 1
achan = 0
dchan = 1
function _step(t)
  if not song[pos] then
    return sys.exit()
  end
  for chan = 0, 3 do
    audio.channelfreq(chan, tone2freq(song[pos]))
  end
  if song[pos] ~= song[pos - 1] then
    vol = 63
  end
  for chan = 0, 3 do
    audio.channelvolume(chan, 0)
  end
  audio.channelvolume(achan, vol)
  achan = achan + dchan
  if achan == 0 then
    dchan = 1
  end
  if achan == 3 then
    dchan = -1
  end
  if vol > 0 then
    vol = vol - 10
  end
  sys.write(lyrics[pos])
  pos = pos + 1
end

lyrics = { "D","a","i","s","y",", ","D","a","i","s","y",",\n",
  "Give ", "me ", "your ", "an", "sw", "er, ", "do", "!", "", "", "", "\n",
  "I", "'", "m ", "ha", "l", "f ", "c", "r", "a", "z", "y", ",\n",
  "All ","for ","the ","lo","ve ","of ","y","o","u","!","\n",
  "It ","won't ","be ","a ","sty","l","ish ","mar","riage",",","","\n",
  "I ","can","'t ","af","fo","rd ","a ","car","riage",",","","\n",
  "But ","you","'ll ","look ","sweet"," ","o","n"," ","the ","seat\n",
  "Of ","a ","bi","cy","cle ","bu","ilt ","for ","two","!","\n","\n"
}
song = {
  27,  27,  27,  24,  24,  24,  20,  20,  20,  15,  15,  15, -- Daisy, Daisy,
  17,  19,  20,  17,  17,  20,  15,  15,  15,  15,  15,  15, -- Give me your answer, do!
  22,  22,  22,  27,  27,  27,  24,  24,  24,  20,  20,  20, -- I'm half crazy,
  17,  19,  20,  22,  22,  24,  22,  22,  22,  22,  22, -- All for the love of you!
  24,  25,  24,  22,  27,  27,  24,  22,  20,  20,  20,  20, -- It won't be a stylish marriage,
  22,  24,  24,  20,  17,  17,  19,  17,  15,  15,  15,  14, -- I can't afford a carriage,
  15,  20,  20,  24,  22,  22,  15,  20,  20,  24,  22, -- But you'll look sweet on the seat
  24,  25,  27,  24,  20,  22,  22,  15,  20,  20,  20,  20,  20,  20 -- Of a bicycle built for two!
}