PURPOSE: To generate a musical sound with an accurate sound pitch by previously discriminating and inspecting the stretched state of a string before a performance and converting a new basic cycle into sound pitch designating data tuned based on the discriminated result of the string state when the new basic cycle is extracted during the sounding state of the string.

CONSTITUTION: Before the performance, when the string is touched at its determined string pressing position, the stretched state of the string related to tuning to be a reference is previously discriminated and inspected by a string state inspecting means 5 based on the basic cycle of a string oscillation extracted in a pitch extracting means 4. Further, when the starting of the sounding of the string is instructed, the basic cycle extracted by the pitch extracting means 4 is converted 11 into the sound pitch designating data tuned based on the discriminated result of the string state, and the sound pitch in an initial stage is controlled. When the new basic cycle is extracted in the pitch extracting means 4 after the starting of the sounding of the string is instructed, the cycle is converted 11 into sound pitch designating data tuned based on the discriminated result of the string state in response to the extraction, and the sound pitch in an after stage is controlled. Thus, the musical sound with accurate sound pitch can be generated.