Electronic Musical Instrument and Electronic Musical Instrument System

Provided is an electronic musical instrument. The electronic musical instrument is configured to generate an internal acoustic signal; generate a sound generation instruction signal; output the sound generation instruction signal to an external sound source configured to generate an external acoustic signal; switch a first state in which the external acoustic signal is generated by the external sound source in response to the sound generation instruction signal, to a second state in which the internal acoustic signal is generated in response to the sound generation instruction signal; and, when the first state is switched to the second state, set a mode of the internal acoustic signal such that the internal acoustic signal is generated with a mode having a predetermined degree of similarity to a mode of the external acoustic signal generated in the first state.