I am little confused by the article because it sounds like they are describing "pulse width" which is a common parameter on analog and digital synthesizers to change the character of the square wave. A square wave with a low pulse width will sound thinner than one with a high pulse width, and layering square waves with different pulse widths gives you a pleasant phasing effect.
Based on some cursory research, however, it seems that duty cycle is different than pulse width, so now I am unsure if they are trying to use duty cycle variation to implement pulse width modulation (PWM) or if they are doing something else entirely.
Based on some cursory research, however, it seems that duty cycle is different than pulse width, so now I am unsure if they are trying to use duty cycle variation to implement pulse width modulation (PWM) or if they are doing something else entirely.