Lfos; Memories; Summary - Novation X-Station User Manual

SYNTHESIS TUTORIAL

LFOs

Like the Envelope Generators, the LFO section on a synthesizer is a
Modulator. That is to say, instead of forming a part of the sound syn-
thesis process, it is used instead to change (modulate) other synthesiz-
er sections. For example, altering the Oscillator pitch or Filter cutoff fre-
quency.
Most musical instruments produce sounds that vary not just in volume
but also in pitch and timbre. Sometimes this variation can be quite sub-
tle, but still contribute greatly towards shaping the final sound.
Where an Envelope is used to control a one-off modulation which
occurs during the lifetime of a single note, LFOs modulate by using a
cyclic repeating wave pattern. As discussed earlier, Oscillators produce
a constant waveform which can take the shape of a repeating sine
wave, triangle wave etc. LFOs produce waveforms in a similar way, but
at a frequency normally too low to produce an audible pitched vibration
that the human ear can perceive. In fact, LFO actually stands for Low
Frequency Oscillator.
As with an Envelope, the waveforms gener-
ated by the LFOs may be fed to other parts
of the synthesizer to create the desired
movements in the sound.
There are two independent LFOs available
which may be used to modulate different
synthesizer sections and run at different
speeds. Use the LFO SELECT button to
select LFO 1 or LFO 2 for editing.
A typical waveshape for an LFO would be a Triangle wave.
Pitch
Time
Imagine this slow moving wave being applied to an Oscillator's pitch.
The result would be that the pitch of the Oscillator slowly rises and falls
above and below its original pitch.
This would simulate, for example, a violinist moving a finger up and
down the string of the instrument whilst it is being bowed. This subtle
up and down movement of pitch is referred to as the 'Vibrato' effect.
Similarly, if the same LFO were applied to the Filter Cutoff frequency
instead of the Oscillator pitch, a similar wobbling effect known as 'wow-
wow' would be heard.
As well as LFOs being available to modify (or more commonly known
as Modulate) different sections of the synthesizer, additional Envelopes
may also be used simultaneously.
Clearly, the more Oscillators, Filters, Envelopes and LFOs there are in
a Synthesizer, the more powerful it becomes.
LFOs - Memories - Summary

Memories

The first generation of synthesizers, produced many years ago were
large modular machines where each part of the synthesizer was
housed in a separate unit (block). These blocks could only be physically
connected together by combinations of cables known as patch leads. A
typical sound produced by this method would often involve connecting
dozens of patch leads.
Every time a new sound was required, the leads would have to be
physically disconnected and reconnected. The positions and connec-
tions of the leads would have to be noted down on paper if there was to
be any hope of creating that particular sound ever again ! If not recon-
nected in exactly the same way, the sound would be lost forever.
Modern machines such as the Novation KS 4 / KS 5 have all the blocks
in one compact unit and the sound generating or modifying blocks are
arranged in a sensible fashion. Front panel switches and knobs deter-
mine how each block functions and where the sound modifying blocks
such as the LFOs and Envelopes are routed, instead of having to physi-
cally connect them externally with cables.
Additionally, The settings of these front panel controls (which of course
determine the current sound or 'patch') may then be stored in memory
locations in the machine which can be recalled at any time.

Summary

An Analogue synthesizer can be broken down into five main sound
generating or sound modifying (modulating) blocks.
1 Oscillators that generate Waveforms at a certain
pitches.
2 A Mixer that mixes the outputs from the Oscillators
together.
3 A Filter that removes certain harmonics, which changes
the characteristic or timbre of the sound.
4 An Amplifier that is controlled by an Envelope
generator. This alters the volume of a sound over
time when a note is played.
5 LFOs and Envelopes that can be used to modulate
any of the above.
Much of the enjoyment to be had with a Synthesizer is with experiment-
ing with the factory preset sounds and creating new ones. There is no
substitute for 'hands on' experience. Experiments with altering knobs
and switches will eventually lead to a fuller understanding of how the
various controls alter and help shape new sounds.
Armed with the knowledge in this chapter, and an understanding of
what is actually happening in the machine when tweaks to the knobs
and switches are made, the process of creating new and exciting
sounds will become easy - Have fun.
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