The TIA (as seen by the programmer)
11.0 Sound
There are two audio circuits for generating sound. They
are identical but completely independent and can be
operated simultaneously to produce sound effects through
the TV speaker. Each audio circuit has three registers
that control a noise-tone generator (what kind of sound), a
frequency selection (high or low pitch of the sound), and a
volume control.
11.1 Tone
The noise-tone generator is controlled by writing to the 4
bit audio control registers (AUDC0, AUDC1). The values
written cause different kinds of sounds to be generated.
Some are pure tones like a flute, others have various
"noise" content like a rocket motor or explosion. Even
though the TIA hardware manual lists the sounds created by
each value, some experimentation will be necessary to find
"your sound".
11.2 Frequency
Frequency selection is controlled by writing to a 5 bit
audio frequency register (AUDF0, AUDF1). The value written
is used to divide a 30KHz reference frequency creating
higher or lower pitch of whatever type of sound is created
by the noise-tone generator. By combining the pure tones
available from the noise-tone generator with frequency
selection a wide range of tones can be generated.
11.3 Volume
Volume is controlled by writing to a 4 bit audio volume
register (AUDV0, AUDV1). Writing 0 to these registers
turns sound off completely, and writing any value up to 15
increases the volume accordingly.