COSC 4P98 Assignment 3
Pure Data Composition
By Nick Harman
Title: Robot
Apologizes
�Robot Apologizes� is made from three separate sources of sound. The left stereo channel is dominated by the Robot Vocals instrument, which sounds like either
�a computer doing some tough work or a robot apologizing to its boss.� The �instrument� is made by frequency modulating a carrier sine wave (20-30Hz) using random number
generators as inputs. The change in modulator parameters is triggered by a metronome that sends an activation pulse every 125ms. The amplitude of the robot voice is controlled with a knob, as
sometimes it mumbles.
Robot Vocals Instrument Data Flow Chart
The output
on the left channel looks very much like amplitude modulation to me at times,
but this may be due to the presence of the �wub�
added to both channels which is described later.
The right channel of the recording is the output of granular synthesis performed on a clip of ELO�s �Twilight�. The result sounds nothing at all like the source material, likely due to the
Parameters controlling the granular synthesis process. The sound is that of the robot�s boss, whatever kind of creature it might be. The only way to describe the sound is �fuming�, like listening to hot gas� from underground. The parameters to the granular synthesis engine (provided via a tutorial from the Pd website) are grain playback speed and pitch, which can be controlled independently.
Finally, a low frequency background �wub� is heard on both channels. It was added in an attempt to make the composition more musical, as a periodic beat of sorts. The frequency is controlled by feeding a midi note through a midi-to-audio converter, and using that value to set the frequency of the oscillator generating the hum. Below is the �code� for the Pure Data composition, with each separate part outlined.
References
Cheetomoskeeto. �PURE DATA: 21 Beginning FM Synthesis�. Youtube video. http://www.youtube.com/watch?v=DgeTHuDSgC0&list=PL12DC9A161D8DC5DC.
�Granular Synthesis�. Pd-tutorial. n.p. Web.19 Mar 2014. http://www.pd-tutorial.com/english/ch03s07.html.
Electric Light Orchestra. �Twilight�. Time. Jet Records, 1981. CD.