The square wave can be reshaped to make the waveform cycles, or pulses, more rectangular, by using a pulse width modulation (PWM) control. The more rectangular the wave becomes, the more nasal it sounds. When modulated in this way, the square wave is known as a pulse wave, and contains fewer harmonics. It can be used for reeds, basses, and brass sounds.
Blue noise: Blue noise is inverse pink noise, and increases the level of all frequencies in higher octaves by 3 dB.
Control Surfaces Support Guide: PDF