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Description of the SimpString object

The SimpString object is a subclass of STK Instrmnt class, which is documented in the STK Class Documentation. Instrmnt is in turn a subclass of Stk--the base class for nearly all STK classes having to do with creating or processing sound samples.

The SimpString object uses the following additional STK classes:

The interpolated delay is the main string model (a digital waveguide model for one plane of transverse string vibration). The non-interpolated delay line is used to implement a feedforward comb filter which simulates pick position (see §4.9.1).

The second-order FIR digital filter simulates one period's worth of losses in the string due to yielding terminations and other sources. It is typically computed from recorded plucked-string data using analysis software written in matlab (see §4.10).

In addition to the FIR ``loop filter'', there is an additional loopGain parameter in series with the loop filter which affects the string decay rate in a frequency-independent manner. While a uniform scaling of the FIR filter coefficients would also accomplish this, it is convenient to leave the FIR filter unchanged and have a single parameter controlling the overall decay rate.

When SimpString is ``instantiated'', the SimpString(lowestFreq) function is called. This function computes the maximum delay-line length, initializes all of its ``instance variables'' declared in SimpString.h, and instantiates and configures its component delay lines, as well as its loopFilter..

The setFreq function sets the current delay-line length to yield the requested fundamental frequency.


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[How to cite and copy this work] 
``Physical Audio Signal Processing for Virtual Musical Instruments and Digital Audio Effects'', by Julius O. Smith III, (December 2005 Edition).
Copyright © 2006-07-01 by Julius O. Smith III
Center for Computer Research in Music and Acoustics (CCRMA),   Stanford University
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