In general, digital waveguide models of string instruments make use of allpass delay-line interpolation techniques because FIR filter techniques result in too much high-frequency attenuation.
The delay-line lengths necessary to produce very high fundamental frequencies may sometimes become too short for a given implementation. This problem could especially occur in conjunction with vectorized computational structures.
The fundamental frequency of the highest piano note (C8) is 4186 Hz. At a sample rate of 44100 Hz, only four (unstretched) partials will possibly fall within the range of human hearing.
Thus, for such high notes, one can instead model each partial with a separate second-order digital resonance filter. The model then consists of several resonance filters combined in parallel.