Click above to get retro games delivered to your door ever month!

  The timer controls the speaker by sending periodic signals that pulse the
  speaker in and out. You can do the same thing with a program that sends in
  or out signals directly to the speaker. Do this by setting bit 0 of port
  61H (decimal 97) to 0 to turn the speaker off and then alternately setting
  bit 1 on and off to pulse the speaker. When you use this method, the speed
  of the program determines the frequency of the sound; the faster the
  program executes, the higher the pitch. The following BASIC program is an
  example of this method:

  10 X = INP (&H61) AND &HFC   ' read port value, turn off bits 1 and 0
  20 OUT &H61, X               ' pull speaker in
  30 OUT &H61, X OR 2          ' push speaker out
  40 GOTO 20

  The actions in lines 20 and 30 pulse the speaker in and out. Each one is a
  half-cycle, and the two together produce one complete sound cycle.

  This example runs as fast as BASIC can process it, producing as high a
  note as possible. If you needed more range in your application, you could
  use a faster language and insert deliberate delays equal to half the
  frequency cycle time between each complete cycle (half the cycle time,
  because each ON or OFF operation is a half-cycle). No matter what language
  you use, you must include a duration count to end the sound. To produce
  different sounds at a particular frequency, such as clicking or buzzing
  sounds, just vary the delays between pulses.

  Despite all these wonderful possibilities, generating sounds through the
  speaker by direct program action is not a good way to make sounds. It has
  three big disadvantages compared to the use of the timer:

  .  A program requires the constant attention of the CPU, so the computer
     has a hard time getting any other work done.

  .  The frequency is at the mercy of the speed of the computer; that is,
     the same program would make a lower or higher sound on a slower or
     faster model.

  .  The clock-tick interrupts interfere with the smoothness of the sound,
     making a warble. The only way to avoid this is to suspend the clock
     tick by disabling the interrupts--and that disrupts the computer's
     sense of time.

  As far as we know, there is only one advantage to making sounds using the
  direct method: With the proper control over the program delays, the direct
  method lets you make a low-fidelity polyphonic sound. Be forewarned,
  though, that this requires some very clever and tedious programming and,
  all in all, may not be worth the trouble.