interpolating comb filter
hcomb() is a feedback loop which will store and feedback the signal continuously. Older inputs will decay over a specified reverberation time. Any frequencies in the input signal whose length in samples is close to an integral number of the number of samples in the loop will be resonated since there will be less cancellation. This represents an improvement over comb in that the quantization of looptime as it becomes shorter due to the integer sample length of the loop is compensated for so that it may be precisely tuned, even up to Nyquist. This loop must first be initialized with a call to hcombset(). which intializes an array for use with an hcomb() filter. Note that this is a fortran sub- routine and thus must contain arguments passed by address, and the underscore following its name.
loopt is equal to 1/hz and array must be dimensioned at (loopt * sr