Arguments: Frequency, Amplitude, Pulse Width
The ugen blsquare is a band-limited square wave generator. In addition to having frequency and amplitude control, there is also a modulatable pulse width parameter. This parameter should be in range 0-1, not including 0 or 1 exactly. The example below shows blsquare with a modulated pulse width.
200 0.3 # LFO modulating pulse width 0.1 1 sine 0.01 0.99 biscale blsquare