instrument’s tone. You will hear the level of each of the 8 lters
being turned up and down automatically in sequence by the
Animation at a tempo determined by the RATE control. Note that
changing the ENVELOPE control affects the shape that turns the
lters up and down. The PATTERN rotary switch selects different
patterns that dictate the sequence that turns the lters up and down
automatically. The MIX control is used to blend the direct sound of
your instrument with the effected sound.
8. In the next sections we’ll explain exactly how the Bass MuRF’s
lters work and what the Animation does. For now, understand the
controls by experimenting with different settings.
FREQUENCIES and FILTERS
Let’s start with some denitions. Please read this section
carefully, as it will help you to understand the basic ideas behind
the MF-105B Bass MuRF’s lters.
Sound is a vibration of the air. The speed of vibration is called
the frequency. It is measured in Hertz (Hz). One Hz is one
vibration per second. We hear vibrations from 20 Hz to 20,000 Hz.
Musical sounds generally have many frequency components.
They’re called harmonics, or overtones, or partials. They are
what give a sound its characteristic tone color, or timbre. A graph
showing the strength of each of a sound’s harmonics is called
a spectrum. A typical spectrum of a musical sound is shown in
Figure 3 - Typical spectrum of a musical sound.
Figure 3.
A lter is a signal-
modifying device that colors
a sound by emphasizing
some parts of the audio
spectrum and attenuating
(cutting down) other parts. In general, a lter has a ‘quality’ of
its own which is superimposed on the tone color of the original
