A real-time Khim sound synthesizer using IIR resonator implemented with a DSP board

This paper presents a real-time sound synthesis of a musical instrument, named "Khim", one of popular kinds of traditional string instruments in Thailand. An approach of spectral modeling for synthesizing the Khim sound was implemented with a TMS320C6713 DSP board. Due to resource limitation of the DSP board, such as limited memory and only 4 external interrupts available, but up to 21 sounds of Khim pitches from vibration of 42 strings were needed to be synthesized, challenge occurred for the design of the real-time synthesizer. By using approximation of dominant frequency components and applying digital IIR resonators implemented with the DSP processor, the Khim sounds were successfully synthesized in real-time without significant difference from the original. An algorithm for controlling the key selection, implemented with another microprocessor, allowed the synthesizer to have enough input keys. The constructed synthesizer was fast responsive and since it had two input keys for a pitch, it allowed fast and continuously-striking sounds to be generated with unnoticeable latency.