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5/3/2018
frequencies, called the modes. When we pluck a string, strike a drum or blow in a tube, the short burst of
energy of the blow/impact contains many frequencies. Some of these fall outside of the modes, and are
absorbed. Some of these excite the modes, producing a stable, pitched sound. Each mode corresponds to
a harmonic or partial in the spectrum of the sound, and is modelled by a band-pass filter. The Q factor of
the filter determine how sustained the oscillations of the corresponding partial are. Various materials or
structures are characterized by different relationships between the frequencies of their modes, which
Rings recreates.
Sympathetic strings
Some interesting string instruments (such as the sitar or sarod), make use of strings that are not directly
struck/plucked by the musician, but which are just responding to vibration of the other strings, and add
extra overtones or undertones to it. Rings simulates this phenomenon with a bunch of virtual strings
(made with comb filters), allowing the addition of extra tones to an incoming audio signal. The tuning ratio
between these strings can be altered.
Modulated/inharmonic string
This last method is perhaps the most familiar (in appearance!), since it is based on the extended Karplus-
Strong method: the excitation signal is sent to a comb filter with an absorption filter, simulating the multiple
reflection of a wave propagating on a string and being absorbed at its ends. However, to bring more
variety to the sound, Rings adds three extra ingredients to this classic: a delay-compensated all-pole
absorption filter creating more drastic plucking effects, delay time modulation emulating the sound of
instruments with a curved bridge (like the sitar or tanpura), and all-pass filters in the delay loop, shifting
the position of the partials and recreating the tension of piano string or completely bonkers inharmonic
timbres.
Making the right connections
Ideally, Rings would need three input signals:
A trigger signal on the
that a new note is starting.
A CV signal on the
V/OCT
An audio signal on the
Because it might not always be possible to get these three signals in your setup, Rings makes the
following assumptions:
First, if nothing is patched in the
note is strummed. This excitation signal is either a low-pass filtered pulse, or a burst of noise depending
on the resonator type.
Secondly, if nothing is patched in the
should be strummed either by:
Detecting note changes on the
Detecting sharp transients within the
If there should be one take-home (take-to-the-studio?) message from this, it is that you can perfectly play
Rings with just one CV output taken from a sequencer or S&H module: the note changes on the CV input
will be interpreted as note changes; and the module will produce a suitable excitation signal internally for
these note changes to be heard!
CONTROLS, INPUTS AND OUTPUTS
https://mutable-instruments.net/modules/rings/manual/
STRUM
input, which indicates that the currently playing note should fade away, and
input, which controls the frequency of the note.
IN
input, which will hit, strike or caress the resonator.
IN
audio input, the module will synthesize an excitation signal whenever a
STRUM
V/OCT
input, or
IN
audio signal if nothing is patched in the
Mutable Instruments | Rings
audio input, the module will determine that a new string
V/OCT
input.
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