I once wrote a program in BASIC (on my C64) which would make such a display (it's straightforward). I lost that program, but recreated a lookalike in Python:

                        --                   --
                     ---                       ---
   ------------------                             -------------
                       --------------------------
          -------------   ------------------     -------------
   -------            ----   -              -------           -
              --------   -    -                    -------
   -----------          -      --------                   -----
                   -----       -       ---------
           --------    -        -               --------
   --------     -------          -----------            -------
      ----------             -------        -----------
   ---               -     --       -------            --------
                    -    --         --     -
                   -   --          -        -
   ----------------  --           -          ------------------
                  ---            -            -
   ---------------              -              ----------------
                               -                -
                       -----------------         --
   --------------------      ------     ------     ------------
           ------           -      --         ------
   --------            -----       ----             -----------
                -------  -       --   -------
          ------        -       -       -    -------
   -------            --       -         --         -----------
                    --        -            -
   -----------------        --              -------------------
                           -      -----      --
                         --     --     --      --
   -----------------------------         --      --------------
    -----------               -           -----------
   -                        --              -        ----------
                          --                 --
                        --                     --
   ---------------------                         --------------

heuh... it looks a bit horrible in ASCII art ;-)

    import random
    import math

    canvh = 40
    canvw = 60
    tracecount = 16
    canvas = [[' ' for col in xrange(canvw)] for row in xrange(canvh)]

    def randomtrace():
        sigma = random.uniform(4, 20)
        mu = random.gauss(canvw/2, canvw/20)
        k = canvw / (sigma * math.sqrt(2*math.pi))
        s = -1.0 / (2 * sigma * sigma)
        amp = 2.0
        tr = [amp * k * math.exp(s * (x - mu)*(x - mu)) for x in xrange(canvw)]
        # TODO: Random permutations, or Perlin noise.
        return tr

    for t in range(tracecount):
        if t == 0 or t == tracecount - 1: 
            continue
        y = t * canvh / tracecount
        trace = randomtrace()
        for x, t in enumerate(trace):
            t = int(t)
            top = y - t
            if top >= 0:
                canvas[top][x] = '-'
            for i in range(t):
                top += 1
                if top >= 0:
                    canvas[top][x] = ' '

    for row in canvas:
        line = "".join(row)
        print "  ", line