Commodore 128 Programmer's Reference Manual page 355

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SOUND AND MUSIC ON THE COMMODORE 128 345
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SOUND AND MUSIC
IN C128 MODE
BACKGROUND:
THE CHARACTERISTICS OF SOUND
Every sound you hear is actually a sound wave traveling through the air. Like any wave,
a sound (sine) wave can be represented graphically and mathematically (see Figure
Figure 11-4. Sine Wave
The sound wave moves (oscillates) at a particular rate (frequency) which deter
mines the overall pitch (the highness or lowness of the sound).
The sound is also made up of harmonics, which are accompanying multiples of the
overall frequency of the sound or note. The combination of these harmonic sound waves
give the note its qualities, called timbre. Figures 11-5 shows the relationship of basic
sound frequencies and harmonics.
-RESULTANT WAVE
-FUNDAMENTAL (1ST HARMONIC)
2ND HARMONIC 3RD HARMONIC
Figure 11-5. Frequency and Harmonics
The timbre of a musical tone (i.e., the way a tone sounds) is determined by the
tone's waveform. The Commodore 128 can generate four types of waveforms: triangle,
sawtooth, variable pulse and noise. See Figure 11-6 for a graphic representation of these
four waveforms.
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