
via AH regarding the following question:
"Does anyone know the formula for calculating the resulting harmonics the formula for calculating the resulting harmonics of a pulse wave when the pulse width is varied? In other words, a square wave (or pulse wave with 50% duty cycle) has only the odd-numbered harmonics present; how do you determine the harmonics present when the duty cycle is 25%, or any other value?"
Dave Manley followed up with a link to this site.
"This brings us to the last member of the Fourier transform family: the Fourier series. The time domain signal used in the Fourier series is periodic and continuous. Figure 13-10 shows several examples of continuous waveforms that repeat themselves from negative to positive infinity."
Update: also see this Synth Secrets article on Sound on Sound.