# Main Title (Terminator 2 Theme) by Brad Fiedel - https://lab.glossema.dev/play/judgement-day/code
# It plays the notes of https://lab.glossema.dev/play/judgement-day, tone for tone.
# The opening of the main title of Terminator 2: Judgment Day (1991): four bars of the ostinato
# alone, then the theme's first statement over it, and one last bar of the arrangement's own.
# Here it runs as a step sequencer on one speaker: 24 steps to the bar, six to the beat, a unit
# of 87 ms that broadens to 88 for the close. The ostinato is a pattern of hits on D3, the tune
# a lane of note letters an octave above the film's. A hit takes the front of the tune's slot,
# and the tune sounds on for the rest.
{
  # the ostinato: a hit on each x of the bar's 24 steps.
  # The intro plays the same figure, cut after five hits
  :local ostinato "x.x...x...x.x...x...x..."
  :local intro ([:pick $ostinato 0 13] . "...........")

  # the tune's notes in Hz, one letter each: capitals D4 to G4, small letters C5 to A5.
  # A lane has a character a step: a letter where a note begins, a dash (0) where none does
  :local notes {"-"=0; "D"=294; "E"=330; "F"=349; "G"=392; "c"=523; "d"=587; "e"=659; "f"=698; "g"=784; "a"=880}

  # under the intro the tune is silent
  :local silence "------------------------"

  # the theme: three phrases climb D, E, F from the same two written bars and end apart,
  # on the low F held, on A stepping down to G, on the low G held
  :local opening {"d--e--f-----------------"; "------------e-------c---"}
  :local endings {
    {"F-----------------------"; "------------------------"};
    {"a-----------------------"; "g-----------------------"};
    {"G-----------------------"; "------------------------"}
  }

  # the close sinks back towards D: the low F held into a short D, then F and E
  :local close {"F-----------------------"; "--------------------D---"; "F-----------------------"; "E-----------------------"}

  # share: the hit, paid out of the tune's slot. It sounds 30 ms and takes 40,
  # and the tune has the rest: a note that begins here, the held note struck again, or silence under the intro
  :local share do={
    :local rest ($span - 40ms)
    :beep frequency=147 length=30ms
    :delay 40ms
    :if ($new > 0) do={
      :beep frequency=$new length=$rest
    } else={
      :if ($held > 0) do={
        :beep frequency=$held length=$rest
      }
    }
    :delay $rest
  }

  # the form: each part's line on the terminal, its unit, its hits and its bars of tune
  :local form {
    {title="Ostinato"; unit=87ms; hits=$intro; bars={$silence; $silence; $silence; $silence}};
    {title="Theme, phrase 1 of 3"; unit=87ms; hits=$ostinato; bars=($opening, ($endings->0))};
    {title="Theme, phrase 2 of 3"; unit=87ms; hits=$ostinato; bars=($opening, ($endings->1))};
    {title="Theme, phrase 3 of 3"; unit=87ms; hits=$ostinato; bars=($opening, ($endings->2))};
    {title="Close"; unit=88ms; hits=$ostinato; bars=$close}
  }

  # the scheduler walks each bar step by step, keeping the tune's sounding note
  :local held 0
  :foreach part in=$form do={
    :put ($part->"title")
    :local unit ($part->"unit")
    :local hits ($part->"hits")
    :foreach tune in=($part->"bars") do={
      :local steps [:len $tune]
      :for step from=0 to=($steps - 1) do={
        :local hit ([:pick $hits $step] = "x")
        :local new ($notes->[:pick $tune $step])
        :if ($hit || ($new > 0)) do={
          # the slot runs to the next hit, the next note or the bar line
          :local next $steps
          :local ahead ($step + 1)
          :while ($ahead < $next) do={
            :if (([:pick $hits $ahead] = "x") || ([:pick $tune $ahead] != "-")) do={ :set next $ahead }
            :set ahead ($ahead + 1)
          }
          :local span ($unit * ($next - $step))
          :if ($hit) do={
            $share new=$new held=$held span=$span
          } else={
            # a note with no hit in front has its whole slot
            :beep frequency=$new length=$span
            :delay $span
          }
          :if ($new > 0) do={ :set held $new }
        }
      }
    }
  }

  # the arrangement's own last bar: one more hit, and the tune steps down to D4 for 1.5 s
  $share new=($notes->"D") span=1540ms
}