Most of these applications employ this one weird trick to get digitized sound out of the speaker: https://en.wikipedia.org/wiki/PC_speaker#Pulse-width_modulatio

Most of these applications employ this one weird trick to get digitized sound out of the speaker: https://en.wikipedia.org/wiki/PC_speaker#Pulse-width_modulation https://en.wikipedia.org/wiki/PC_speaker#Pulse-width_modulat... The result is 6 bits of resolution, along with a high pitched squeak during playback, depending on the output circuitry and speaker characteristics (it's less noticeable when a low-pass filter is added).