2.1.2.
Pitch Modulation
BoomTschak’s BEND DECAY and BEND SHAPE knobs control an envelope generator which
varies the pitch of the oscillator. The pitch of many real-world drums starts slightly sharp and
bends downward as the sound fades. A few percussion instruments, such as tablas, can be
made to bend upwards in pitch. Electronic drums, unconstrained by physical mechanics, can
bend wildly.
The BEND DEPTH knob controls how much the oscillator’s pitch changes. It is a bidirectional
control; if placed at its center position, the pitch will be the same for the duration of the sound. If
you turn the knob clockwise, the pitch will start sharp and bend downwards. Turn the knob the
other direction to make the pitch bend upwards.
Besides the obvious creation of dramatic frequency swoops, the pitch bend controls can also
add character to the attack of the sound. With the oscillator set to a fairly low frequency, try
turning the BEND DECAY and BEND SHAPE knobs fully anti-clockwise, then slowly turn the
BEND DEPTH knob clockwise from its center position.
2.1.3.
Pitch Input Jack
The frequency of the oscillator can also be controlled directly by a signal applied to the PITCH
INPUT jack. The VCO responds to input voltages with the usual convention of a change of one
volt producing a change of one octave. Yes, this means that you can play melodies or bass lines
with BoomTschak.
