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 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.